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Poverty and climate change: Natural disasters, agricultural impacts and health shocks

Stephane Hallegatte, Mook Bangalore, Laura Bonzanigo, Marianne Fay, Tamaro Kane, Ulf Narloch, Julie Rozenberg, David Treguer and Adrien Vogt-Schilb The World Bank Group

The international community aims to eradicate extreme poverty and to do so in a sustainable manner. This chapter suggests that climate change poses a major obstacle to this challenge. Climate-related shocks and stresses – from natural disasters to agricultural impacts and health shocks – already prevent households from escaping poverty. Poor people are disproportionally vulnerable to these shocks because they are more exposed and lose more when affected. Climate change will worsen the situation, making it more difficult to eradicate poverty in a sustainable manner. Many policy options are available to help reduce poor people’s risk and vulnerability, including building climate-smart infrastructure, providing universal health coverage, implementing social safety nets that can be scaled-up and rapidly targeted towards people affected by a shock, and facilitating migration. With regards to natural hazards, agricultural impacts and health shocks, climate change makes existing priorities more urgent. If addressed correctly, this urgency can turn into an opportunity to reduce both current poverty and future climate vulnerability, before most of the impacts of climate change materialise.

The impacts of climate change.
Estimates of the economic cost of climate change have always attracted interest and debate among policymakers and the public. These estimates, however, have mostly been framed in terms of the impact on country-level or global GDP, which does not capture the full impact of climate change on people’s well-being. One reason is that such estimates do not reflect the distribution. The distribution of climate impacts – that is, which countries, regions and people are hit – will determine their effects on well-being. Three-quarters of global income belongs to North America, Europe, and East Asia; the other regions are economically much smaller, and in particular, sub-Saharan Africa, which only generates 2% of global income (World Bank 2015). The location of impacts to GDP therefore matters. Equally important is the fact that the impacts of climate change will be highly heterogeneous within countries. If the impacts mostly affect low-income people, the welfare consequences will be much larger than if the burden is borne by those with a higher income. Poor people have fewer resources to fall back on and lower adaptive capacity. And – because their assets and income represent such a small share of national wealth – poor people’s losses, even if dramatic, are largely invisible in aggregate economic statistics. Investigating the impact of climate change on poor people and on poverty requires a different approach, focused on people that play a minor role in aggregate economic figures and are often living within the margins of basic subsistence. Such an approach was behind a research programme on ‘Poverty and climate change’ at the World Bank, and this chapter is based on some of the programme’s results (for a comprehensive presentation of the results, see Hallegatte et al. 2016). The research starts from the idea that poverty is not static, and poverty reduction is not a monotonic, one-way process. Over time, some people build assets and move out of poverty while others experience shocks and are pulled into poverty. What we call poverty reduction is the net result of these mechanisms. For instance, Krishna (2006) documents poverty dynamics in 36 communities in Andhra Pradesh, India, over 25 years. Each year, on average 14% of households escaped poverty while 12% of non-poor households became poor, so that.

Overall, poverty was reduced by 2% per year. These numbers show that a relatively small change in the flows in and out of poverty has a significant effect on overall poverty dynamics. For instance, increasing the flow into poverty by 10% is enough to halve the rate of poverty reduction. Climate change can affect the flow of people into poverty. In the Andhra Pradesh sample, drought is a major factor – a household affected by drought in the past was 15 times more likely to fall into poverty (Krishna 2006). Droughts may also result in people falling into poverty traps as a result of asset losses. They often affect human capital, especially for children who may be pulled out of school or suffer permanent health consequences (Carter et al. 2007). Even just the risk of drought can lead poor people to invest in low-risk but low-return activities, perpetuating poverty (Elbers et al. 2007). An impact of climate change on drought frequency and intensity could therefore hamper poverty reduction, with more people falling into and fewer people escaping poverty. But droughts and natural hazards are not the only climate-sensitive factors to affect the flows in and out of poverty. Agricultural income and food prices matter, as do health shocks. The next sections investigate the following major channels through which climate change affects poverty dynamics: natural hazards, agriculture and health. Of course, many other factors play a role, but these three channels already have well-documented impacts on poor people and poverty reduction, and will be affected by future climate change.

In some regions, natural hazards such as floods, droughts, and extreme temperatures will increase in frequency or intensity as a result of climate change. The exposure, vulnerability, and lack of adaptive capacity of poor people puts them at particular risk. Regarding exposure, it is often the case that poor people live in risky areas. A number of case studies have examined the exposure of poor and non-poor people to disaster risk, with most finding poor people to be more exposed (Figure 1). For instance, when large-scale floods hit the Shire River Basin in Malawi in January 2015, the areas with the highest exposure were also the poorest (Winsemius et al. 2015).

Middle East and North Africa.

But the relationship between poverty and exposure to risk is not straightforward. Causality runs in both directions: poor people sometimes choose to settle in risky areas where land is available or affordable, and living in risky areas may make people poor when hazards destroy assets and livelihoods. But poor people are not always more exposed; for instance, flood-prone coastal or river areas benefit from low transport costs that attract firms and opportunities and the wealthier populations in a country. In these cases, rich people may be the ones most exposed. In-depth analyses find no systematic overexposure of poor people to floods at the national level, although poor people are often the most exposed within a city or a region (Winsemius et al. 2015). While not systematically more exposed, poor people are certainly more vulnerable when a disaster strikes and lose larger shares of their assets or income. This is because poor people hold a large fraction of assets in material and vulnerable form (rather than as financial savings in a bank), live in lower-quality housing (such as slums), and depend on lower-quality infrastructure (such as non-paved roads). In the small number of surveys that compare asset and income losses of poor and non-poor people after floods and storms, poor people are found to lose a larger share (Figure 2). With regards to droughts, the fact that poor people are more dependent on agricultural income makes them more vulnerable (see Section 3). In the future, these vulnerabilities will evolve as the share of people in agriculture changes and as differences between poor and non-poor people are reduced (for example, in terms of building quality and access to infrastructure).

In addition, poor people often have more limited access to social protection, a factor that makes them more vulnerable after disasters. A consistent finding across countries is that transfers (from social protection and labour markets) received are much lower for poor people (ASPIRE 2015). For example, in Colombia, the poorest 20% receive on average US$0.23 per person per day, while the richest 20% receive $4.60. Even after a disaster, ad hoc schemes to provide compensation have not targeted poor people, as evidenced by the 2005 Mumbai floods (Patankar 2015) and the 2011 Bangkok floods (Noy and Patel 2014). With less income coming from transfers and less savings, poor households are more dependent on their labour income for their consumption, making them more vulnerable to shocks and lost days of work (their inability to smooth consumption can even translate into avoidable health impacts, as discussed in Section 4).

It is therefore no surprise that natural disasters have a well-documented impact on poverty (Karim and Noy 2014). For example, at the municipal level in Mexico, Rodriguez-Oreggia et al. (2013) find that floods and droughts increased poverty by between 1.5% and 3.7% from 2000 to 2005. To compound these effects, disasters often result in reduced food consumption for children as well as interrupted schooling, with likely lifelong impacts such as stunting and reduced earning capacity (Alderman et al. 2006).But looking only at the impact of actual disasters may underestimate the effect of risk on development and poverty. Ex ante, in the presence of uninsured weather risk, poor households engage in low-risk, low-return activities, perpetuating poverty. This ex ante effect, while much less visible, can dominate ex post impacts of disasters (Elbers et al. 2007). While progress has been made in recent years, many poor people remain uninsured and they exhibit lower financial inclusion than non-poor people (FINDEX 2015). Climate change will worsen the frequency and intensity of natural disasters in some regions (IPCC 2014), but future impacts will depend not only on climate change, but also on the policies and actions implemented to manage risk. Land-use planning – especially in growing cities – is critical to ensure that new development is resilient and adapted to a changing climate (Hallegatte et al. 2013).

Early warning systems, hard and ecosystem-based protection against floods, preservation of ground water, and improved building quality for poor people are all policies that can save lives and reduce asset losses. Providing options to poor households to save in financial institutions is critical to protect their savings. Social protection that can be scaled up after a disaster, and targeting instruments that are able to identify affected households and deliver aid in a timely fashion to those who need it can help avoid long-term, irreversible consequences and poverty traps (Pelham et al. 2011).

Agricultural impacts
Climate change will impact agricultural and land productivity, especially for major crops (wheat, rice and maize) in tropical and temperate regions, with higher emissions pathways worsening the impacts (Porter et al. 2014). Under the most optimistic climate scenario – and with CO2 fertilization (an effect that suggests plants can improve photosynthesis and productivity with higher CO2 concentrations) – crop yields may decrease globally by 2% by 2030; but if emissions continue unabated, the reduction could amount to 6% by 2050 and 14% by 2080. And without CO2 fertilization, the impacts may be even more severe, with yields falling by 10% and 33% by 2030 and 2080, respectively (Havlík et al. 2015). But the global impacts will not be uniform across crops and regions. These impacts are also extremely uncertain – they depend on the extent to which CO2 fertilization materialises, the availability of water, and the development of new varieties and techniques better suited to future climates.Productivity impacts will be transmitted through markets, with very uncertain impacts on food prices; the IPCC suggests that global food prices may vary between -30% and +45% (Porter et al. 2014).

Higher food prices would reduce consumption, but modelling exercises show the final effect will depend not only on the change in climate, but also on the socioeconomic context, including GDP growth and access to global food markets. Food security concerns are less in a world with fast economic growth and low poverty (a ‘Prosperity’ scenario) compared to a world with slow growth and high poverty (a ‘Poverty’ scenario). For instance, under RCP 8.5 (a high emissions scenario) without CO2 fertilization, global losses in food consumption are estimated at 2.5% and 4% for 2050 and 2080 in the Prosperity scenario, while the figures are over 4% and 8% in the Poverty scenario (Figure 3).

Any change in food consumption will be particularly severe for poor people, who spend a larger share of their budget on food (62% on average, compared to 44% for non-poor people; see Ivanic and Martin 2014). Poor people in urban areas often have higher shares than rural people, as the latter may produce some of their own food to cover their needs. Increased food scarcity is likely to translate into more ‘food crises’ during which food prices rise rapidly, for instance, due to weather- or pest-related reductions in production in a major producer country. As illustrated by the spike in 2008, such episodes have a major impact on poverty, and studies suggest that future increases will have significant impacts. In the absence of safety nets and economic adjustments, a number of countries – including Guatemala, India, Indonesia, Pakistan, Sri Lanka, Tajikistan and Yemen – could suffer from an increase in extreme poverty of 25 percentage points if faced with a 100% food price increase, with severe impacts in urban areas (Ivanic and Martin 2014).

But for food producers, an increase in food prices is not necessarily a bad outcome. The final impacts will depend on how changes in prices and in productivity balance (an increase in food prices due to reduced productivity does not automatically lead to increased revenues) and on how increased revenues are distributed among farmworkers and landowners (Jacoby et al. 2014). Taking a comprehensive view of farm households (i.e. both their consumption and production), Hertel et al. (2010) argue that such households may benefit from climate impacts if the shock is widespread, farm-level demand for their production is inelastic (while the supply response is low), there are few sources of off-farm incomes, and food represents a relatively small share of expenditures. In some areas, however, transformational change in the production sector will be required. For instance, in Uganda, coffee production is a central activity, employing more than 2 million people and contributing close to US$400 million to the national economy in 2012. But climate change will make growing coffee increasingly difficult in the next decades, making it necessary for the local economy to restructure around a different crop or sector (Jassogne et al. 2013).

Going through such large-scale transformations is highly challenging; in the 1930s, the Dust Bowl eroded large sections of the Great Plains in the US (an area previously renowned for agriculture), and the impacts endured for decades (Hornbeck 2012). Vulnerability to agricultural impacts will be shaped by the future of poverty and by future market structure and access. Evidence suggests that remote markets have higher price volatility (Ndiaye et al. 2015). Enhancing road infrastructure can strengthen links between rural markets and urban consumption centres, stabilising prices. And the share of their income that people spend on food will decrease as people escape poverty, making the consequences of higher food prices more manageable in the future (if poverty decreases as rapidly as expected, and if poverty reduction reaches the remote rural areas where it is largely absent at the moment) (Ravallion 2014).

Health impacts
Health shocks are the leading reason why households fall into poverty (Moser 2008). They affect households through many channels: the direct impact on well-being; the consequences of the death of a family member; loss of income when a family member cannot work; expenses from care and drugs, especially in the absence of health insurance; and time and resources spent on caregiving. This is why the effect of climate change on health is particularly worrisome. Impacts can occur through increased natural disasters, which have well-documented health effects. Disasters directly impact health through fatalities and casualties, particularly in low-income and lower-middle-income countries, which account for only a third of all disasters but more than 80% of all deaths (UNDP, UNICEF, OXFAM and GFDRR 2014). After a disaster, health conditions worsen when there is inadequate food, water and sanitation. The health effects also surge when affected poor households cannot smooth consumption – a drop in income often translates into reduced food intake, with potentially long-term effects on child development, affecting for example future strength, cognitive capacity and earning potential (Alderman et al. 2006).As well as from disasters, health impacts also occur from environmental disruptions to crop productivity and food availability (Smith et al. 2014).

One example is under-nutrition, which is not only influenced by crop productivity and food availability, but also by water quality and access to sanitation. Climate change is expected to increase stunting, with up to 10 million additional children stunted under a base case economic growth scenario in 2050 (Lloyd et al. 2011, Hales et al. 2014) (Figure 4). Some regions will be particularly affected, with cases of severe stunting possibly increasing by up to 23% in sub-Saharan Africa and 62% in South Asia (Lloyd et al. 2011). These trends are all the more alarming considering that moderate stunting increases the risk of death by 1.6 times and severe stunting by 4.1 times (Black et al. 2008). Climate change will also change patterns of vector-, soil- and waterborne diseases, introducing them into new areas (Smith et al. 2014). The combined effects of temperature fluctuation, coastal salinity, humidity, heavy rainfall, flooding and drought can contribute to outbreaks of diseases such as schistosomiasis, cholera, malaria and diarrhoea (Cann et al. 2013, Hales et al. 2014).

All of these diseases affect poor people more than the rest of the population, and children more than adults. They also have an impact on income and economic growth. These micro-level impacts translate into lower macroeconomic growth; Gallup and Sachs (2001) find that countries with intensive malaria grew 1.3% slower than other countries in the period 1965-1990. Estimates suggest that 3% of global diarrhoea cases can be attributed to climate change, and the frequency of malaria cases may increase by up to 10% by 2030 in some regions (WHO 2009). Higher temperatures are one reason for this: a study in Lima, Peru, found a 4% increase in hospital admissions for diarrhoea for each 1°C temperature increase during warmer months, and a 12% increase for every 1°C increase in cooler months (Checkley et al. 2000). We can only begin to measure the global burden of disease from climate change, but observed patterns are worrisome. A recent synthesis of five key aspects – under-nutrition, malaria, diarrhoea, dengue and heatwaves – estimates that under a base case socio-economic scenario and a medium/high emissions scenario, approximately 250,000 additional deaths per year between 2030 and 2050 will be attributable to climate change (Hales et al. 2014). But the future burden of disease will depend on development. Despite rising temperatures in the twentieth century, malaria rates dropped significantly. This is because socioeconomic trends – urbanisation, development, and improvements in health facilities – matter much more for controlling malaria than climate impacts (Gething et al. 2010). Development objectives such as achieving universal health coverage by 2030 could contribute greatly to adapting to climate change impacts on health. In fact, the recently released Lancet report on health and climate change declared that responding to climate change could be “the biggest global health opportunity of the 21st century” (Watts et al. 2015).

How can we achieve low-carbon resilient development?
While climate change impacts poverty, poverty reduction reduces vulnerability to climate impacts. The previous discussion highlights some of the benefits that development and poverty reduction can bring in terms of climate vulnerability. For instance, better social safety nets, improved access to financial institutions and insurance, and reduced inequality would mitigate the impact of disasters, and especially the irreversible impacts on children’s health and education. Improved connection to markets – with better infrastructure and appropriate institutions – would protect consumers against large food supply shocks, and help farmers access the technologies and inputs they need to cope with a different climate. Basic services – for example, improved drinking water and sanitation and modern energy – can also help protect against some of the impacts of climate change, such as waterborne diseases and environmental degradation.

And access to health care has been improving with development and growth in most countries, with the benefits being exemplified by reductions in child mortality and malaria. Most importantly, development and climate mitigation need not be at odds with each other. Evidence suggests that raising basic living standards for the world’s poorest will have a negligible impact on global emissions (Rao et al. 2014, Fay et al. 2015). Initiatives such as the UN’s ‘Sustainable Energy for All’ can improve access to electricity and at the same time be compatible with a warming limit of 2°C (Rogelj et al. 2013). Making mitigation and poverty eradication compatible will require a sequenced approach where richer countries do more, special attention is given to the impacts of land-use-based mitigation on food production, and complementary policies (e.g. cash transfers) are introduced to protect poor people against negative side-effects of mitigation (Fay et al. 2015). In many cases, it will also require richer countries to support poorer countries to provide technologies and financing instruments. The impacts of climate change will increase over time. There is therefore a window of opportunity to reduce poverty now and thereby reduce vulnerability tomorrow. Any climate agreement that aims to be workable and effective should have this goal of reducing vulnerability in mind and be designed in a way that contributes to development and poverty eradication.But not all development pathways reduce climate risks in the same way. Of course, low-carbon development mitigates climate change and reduces risks over the long term, benefiting everybody, particularly the poorest. In addition, resilient development would go further in reducing the impacts of climate change. But what does it entail? From our analysis, a few recommendations emerge:

Many investment and policy decisions have long-term consequences. The effect of transport infrastructure on urban form and economic activity can be observed over long timeframes, sometimes even after the infrastructure has become obsolete (Bleakley and Lin 2010). Policies such as urbanisation plans, risk management strategies, and building codes can influence development for just as long. Therefore, to ensure development is adapted not only to present but also to future conditions, plans must consider the performance of investments and decisions in the short and long term. But doing so is challenged by deep uncertainty – we cannot predict future climate conditions precisely, we do not know which technologies will appear, and we are unsure about socioeconomic conditions and future preferences. There is a risk of locking development into dangerous pathways, for instance by urbanising impossible-to-protect flood plains or by specialising in agricultural production at risk of climate change. To avoid this, the planning process needs to investigate a large range of possible futures, and to make sure it does not create unacceptable risks when climate change and other trends are accounted for, especially if these changes differ from what is considered most likely today (Kalra et al. 2014). Such a robust approach leads to strategies that include safety buffers (e.g. adding safety margins around what areas are considered prone to flooding today), promoting flexibility (e.g. select solutions that can be adjusted over time as more information becomes available), and increasing diversification (e.g. developing the economic sectors that are less exposed to risk).

Improving access to healthcare.
Helping households manage health risks is already a priority, considering the role of these shocks in maintaining people in poverty. Climate change only makes this task more urgent and more important. Skilled health staff, with the right equipment and drugs, need to be available in all areas. But even if health care is available, the ability to afford health care is essential – about 100 million people fall into poverty each year due to having to pay for healthcare (WHO 2008). Increasing healthcare coverage and decreasing out-of-pocket expenses is a smart investment for development and poverty reduction, and would be an efficient tool to reduce climate change vulnerability. Doing so is possible at all income levels. For instance, Rwanda invested in a universal health coverage system after the 1994 genocide, with premature mortality rates falling precipitously, and life expectancy doubling (Binagwaho et al. 2014). Climate change does not dramatically change the challenges for the health sector, but emerging issues and diseases increase the importance of monitoring systems that can identify and respond quickly to new – and sometimes unexpected emergencies.

Provision of well-targeted, scalable safety nets.
Safety nets can help manage weather shocks. During the 1999 drought in Ethiopia, the poorest 40% of the population lost almost three-quarters of their assets (Little et al. 2004). Today, Ethiopia’s Productive Safety Net Program supports 7.6 million food-insecure people and builds community assets to counteract the effects of droughts. The programme has improved food security, access to social services, water supply, productivity, market access, and ecosystems (Hoddinott et al. 2013). Safety nets can also play a critical role in avoiding irreversible losses from under-nutrition, but only if scaled-up and deployed quickly aftershocks and targeted to the poorest and most vulnerable (Clarke and Hill 2013). In addition, the increasing impacts of natural disasters make it essential for safety nets to be able to identify quickly those in need, and to scale-up and retarget support after a shock or disaster (Pelham et al. 2011).

Further, trends in climate conditions and risks mean that some places will become increasingly less suitable for development. As a result, temporary and permanent migration is an important risk-management tool and can be an adaptation option. Independently of climate change, migration plays a key role in the ability of poor households to escape poverty by capturing opportunities for better jobs, higher pay, and improved access to services and education. Climate change may trigger more migration – for instance, if opportunities disappear because of climate impacts (for the example of coffee in Uganda, see Jassogne et al. 2013) – but may also impair migration, for example through increased conflict and exclusion (for an extended review, see Adger et al. 2014). Given the importance of mobility as an instrument for poverty reduction, it is critical that social protection does not lock people into places or occupations from which it will become harder for them to escape poverty. Portability of social protection (geographically and in terms of occupation) is therefore made even more important by a changing climate. With regards to natural hazards, agricultural impacts and health shocks, climate change only makes existing priorities more urgent for many countries. If addressed correctly, this urgency can turn into an opportunity to reduce current poverty and future climate vulnerability simultaneously. Of particular importance are the high economic and health impacts that climate change could have on children. Without action to move towards low-carbon, resilient development now, we may lock ourselves into a future of increased intergenerational transmission of poverty.

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Climate Change Impacts on East Africa

Muawya Ahmed Hussein.
Africa contains about one-fifth of all known species of plants, mammals, and birds, as well as one-sixth of amphibians and reptiles. These species compose some of the world's most diverse and biologically important ecosystems such as savannahs, tropical forests, coral reef marine and freshwater habitats, wetlands and montane ecosystems. These globally important ecosystems provide the economic foundation that many Africa countries rely on by providing water, food, and shelter. However, because of climate change, these ecosystems and the livelihoods that depend on them are threatened. The aim of this paper is to highlight some of the major impacts of climate change on conservation for East Africa countries including Kenya, Tanzania, Uganda and Rwanda. As this paper illustrates, climate change in Africa is not only a conservation problem but is a socio-economic issue that must be dealt with at a global scale.

Climate change is really happening now. The average global surface temperature has warmed 0.8 C in the past century and 0.6C in the past three decades (Hansen et al., 2006), in large part because of human activities (IPCC, 2001). A recent report produced by the U.S. National Academy of Sciences confirms that the last few decades of the 20^th century were in fact the warmest in the past 400 years (National Research Council, 2006). The Intergovernmental Panel on Climate Change (IPCC) has projected that if greenhouse gas emissions, the leading cause of climate change, continue to rise, the mean global temperatures will increase 1.4 – 5.8C by the end of the 21 century (IPCC, 2001).

The effects of climate change such as rising temperature and changes in precipitation are undeniably clear with impacts already affecting ecosystems, biodiversity and people.  In both developed and developing countries, climate impacts are reverberating through the economy, from threatening water availability to sea-level rise and extreme weather impacts to coastal regions and tourism. In some countries, climate impacts affect the ecosystems services that communities are largely dependent upon, threatening development and economic stability. Future impacts are projected to worsen as the temperature continues to rise and as precipitation becomes more unpredictable.

One region of the worked where the effects of climate change are being felt particularly hard in Africa. Because of the lack of economic, development, and institutional capacity, African countries are likely among the most vulnerable to the impacts of climate change (IPCC 2001). Climate change impacts have the potential to undermine and even, undo the progress made in improving the socio-economic well-being of East Africans. The negative impacts associated with climate change are also compounded by many factors, including widespread poverty, human diseases, and high population density, which is estimated to double the demand for food, water, and livestock forage within next 30 years (Davidson et al., 2003).

Observed and Projected Climate Change
Overall Africa has warmed 0.7 Cover the 20^th century and general circulation models project warming across Africa ranging from 0.2C per decade (low scenario) to more than 0.5C per decade (high scenario) (Hulme et al.,2001; IPCC,2001). Hulme et al., 2001, suggest that under intermediate warming scenarios, parts of equatorial East Africa will likely experience 5-20% increased rainfall from December – February and 5-10% decreased rainfall from June-August by 2050 Climatic change of this magnitude will have far-reaching, negative impacts on the availability of water resources, food and agricultural security, human health, tourism, coastal development and biodiversity and are highlighted below.

Water Availability
Arguably one of the most widespread and potentially devastating impacts of climate change in East Africa will be changing in the frequency, intensity, and predictability of precipitation. Changes in regional precipitation will ultimately affect water availability and may lead to decreased agricultural security, human health, tourism, coastal development and biodiversity and are highlighted below.

Projections of climate change suggest that East Africa will experience warmer temperatures and a 5-20% increased rainfall from December –February and 5-10% decreased rainfall from June – August by 2050 (Hulme et al ., 2001; IPCC, 2001). Not only are these changes not uniform throughout the year, but they will also likely occur in sporadic and unpredictable events. It may also be likely that the increased precipitation will come in a few very large rainstorms mostly during the already wet season thereby adding to erosion and water management issues and complicating water management. It is also expected that there will be less precipitation in East Africa during the already dry season, which may cause more frequent and severe droughts and increased desertification in the region.

Recent research also suggests that warming sea surface temperatures, especially in the southwest Indian Ocean, in addition to interannual climate variability (i.e El Nino/Southern Oscillation (ENSO) may play a key role in East African rainfall and may be linked to the change in rainfall across some parts of equatorial-subtropical East Africa (Cane et al. 1986; Pilsnier et al, 2000; Rowe 2001). Warm sea surface temperatures are thought to be responsible for the recent droughts of in equatorial and subtropical Eastern Africa during the 1980s to the 2000s (Funk et al, 2005).  According to the UN Food and Agriculture Organization (FAO, 2004), the number of African food crises per year has water supplies reduce crop productivity and have resulted in widespread famine in East Africa.

In addition to declining moisture needed for pastoral and agricultural activities, the availability of water for human consumption is of paramount concern. Currently, two-thirds of rural Africans and a quarter of urban dwellers in Africa lack access to clean, safe drinking water (Simms, 2005). In Tanzania for example, two of three rivers have reduced flow due to declining regional rainfall, which has had ecological and economic impacts such as water shortages, lowered agricultural production, increased fungal and insect infestations decreased biodiversity and variable hydropower production (Orindi and Murray, 2005). High temperatures and less rainfall during already dry months in the Tanzania river catchments could affect the annual flow to the River Pangani by reductions of 6-9% and to the river Ruvu by 10% (VPO-URT,2003). The Pangani Basin is also fed by the glaciers of Kilimanjaro, which have been melting alarmingly fast and are estimated to disappear completely by 2015-2020 (Thompson et al 2002). The population living around the base of Kilimanjaro uses this meltwater and the fog water from the rainforests that cover the mountain’s flanks for drinking, irrigation and hydropower. The Pangani Basin is one of Tanzania’s most agriculturally productive areas and is an important hydropower production region. Because of this, climate change threatens the productivity and sustainability of this region’s resources, which hosts an estimated 3.7 million people.

Food security
There is a strong link between climate and East African livelihoods and food security highly vulnerable to climate variability such as shifts in growing season conditions (IPCC,2001). Further, agriculture contributes 40% of the region’s gross domestic product (GDP) and provides a living for 80% East Africans (IFPRI,2004). However because the temperature has increased and precipitation in the region has decreased in some areas, many are already being affected. For example, from 1996 to 2003, there has been a decline in rainfall of 50-150 mm per season (March to May ) and a corresponding decline in long-cycle crops (eg, slowly maturing varieties of sorghum and maize) across most of eastern Africa (funk et al; 2005). Long – cycle crops depend upon rain during this typically wet season and progressive moisture deficit results in low crop yields in the fall, thereby impacting the available food supply.

Increased variability (ie deviation from the mean) of crop production is also a major concern of farmers in eastern Africa. Inter-annual climate variability (eg. ENSO) has huge impacts on the region’s climate. Warm ENSO events also referred to as El Nino events produce abnormally high amounts of precipitation in parts of equatorial East Africa and can result in flooding and decreased agricultural yields. Further south, in Zimbabwe, researchers correlated past El Nino events and warm sea surface temperatures in the eastern equatorial pacific with more than 60% of the change between above and below-average agricultural production of maize (Patt et al; 2005).

Climate change may also impact the region’s fisheries. While many tropical fishes have evolved to survive in very warm water, many have a critical thermal maximum and can not survive temperatures that exceed this threshold. For example, spotted tilapia, (Tilapia mariae), native to parts of Africa, prefer temperatures between 25 and 33oC, depending upon acclimation temperature, and have a critical thermal maximum of 37C (Siemien and Stauffer 1989). Though tropical fishes can endure temperatures very near their temperature threshold, a slight (1-2 C) increase in regional temperatures may cause the daily temperature maxima to exceed these limits, particularly for populations that currently exist in thermally marginal habitats (Roessing et al, 2004). However, because there is little data on the ability of this species to adjust their tolerance to water temperature their response to climate change is largely unknown.

An increase in mean temperature may also affect the dissolved oxygen concentrations in the layer of water below the thermocline (hypolimnion) in two ways: increased metabolism of fish and other organisms in a slightly warmer hypolimnion will lead to the faster depletion of the limited oxygen supply, and lake overturn, the primary means of replenishing hypolimnetic dissolved oxygen, will occur less frequently (Fick et al; 2005). The African General Lakes contain deep anoxic hypolimnia of tropical lakes also contain a high concentration of hydrogen sulfide. This chemical compound is a byproduct of anaerobic decomposition of organic matter and is highly toxic to fish. Moderate amounts of mixing allow nutrient influx into the layer of water above the thermocline and benefit fisheries productivity without introducing a high concentration of toxic hydrogen sulfide (Fick et al; 2005) this is demonstrated at the stratified northern end of Lake Tanganyika, Africa, which supports a less productive fishery than the well-mixed southern arm and the main basins (Vuorinen et al; 1999). A comparative study of historical and current levels of primary production in the northern end of Lake Tanganyika indicated that current levels are much lower as a result of strengthened stratification (Verburg et al; 2003). Recent changes in the limnology of lake Victoria have also negatively affected its fishery. In the 1980s decreased turnover in the lake led to low levels and dissolved oxygen and, consequently, fish kills. Stratification in this lake now appears to e permanent (Kaufman et al; 1996).

Human Health
Climate variability has had far-reaching effects to human health, and includes, but is not limited to, the following; heat stress, air pollution, asthma, vector-borne diseases (such as malaria, dengue, schistosomiasis (also referred to as swimmer’s itch or snail fever) and tick-borne diseases), waterborne and foodborne diseases (such as diarrhoea diseases). For this report we concentrate on just two of these effects, malaria and Rift Valley fever; however other health issues are likely to be affected by climate change.

Climate change is expected to exacerbate the occurrence and intensity of future disease outbreaks and perhaps increase the spread of diseases in some areas. It is known that climate variability and extreme weather events such as high temperatures and intense rainfall events, are critical factors in initiating malaria epidemics especially in the highlands of western Kenya, Uganda, Ethiopia, Tanzania, Rwanda and Madagascar (Zhou et al; 2004). While other factors such as topography and health preparedness can influence the spread of malaria, scientists have found a correlation between rainfall and unusually high maximum temperatures and the number of malaria cases (Githiko and Ndegwa, 2001; Zhou et al; 2004). From 1920 to 1950, the highlands of eastern Africa experienced infrequent malaria outbreaks, however, since then the current pattern is characterized by increased outbreak frequencies, expanded geographic range, and increased case-fatality rates (Zhou et al., 2004). The spread of malaria is seasonal and limited to the warm and rainy months; however, changing climate conditions, such as the persistence of warm and rainy days for more of the year can increase the incidence of malaria events (Craing et al., 2004). In addition to longer seasons that are suitable for malaria spread, temperatures have also been warming in formerly cooler, higher elevation East African highlands. Subsequently, these areas are experiencing a spread of malaria in populations that had not previously been frequently exposed to the disease (Patx et al., 2005; Zhou et al., 2004).

Rift Valley Fever epidemics are also correlated to climate variability. Between 1950 and 1988 three quarters of the Rift Valley Fever outbreaks occurred during warm ENSO event periods (i.e., El Nino events). During El Nino, the East African highlands typically receive unusually high rainfall which is correlated with Rift Valley Fever outbreaks (Patx et al 2005).

Extreme Weather Events
Warming temperatures are projected to cause more frequent and more intense extreme weather events, such as heavy rainstorms, flooding, fires, hurricanes, tropical storms and El Nino events (IPCC,2001). Tropical storms can ravage coastal areas and intensive the impacts of sea-level rise by accelerating erosion in coastal areas and by removing protective natural buffer areas that absorb storm energy, such as wetlands and mangroves (Magadza, 2000). Extreme rainfall and subsequent heavy flooding damage will also have serious effects on agriculture including the erosion of topsoil, inundation of previously arid soils, and leaching nutrients from the soil. Regional fluctuations in lake levels are another impact of regional climate variations and are expected to worsen with projected climate change. While land use change can have a dramatic effect on lake levels, climate variability is more unpredictable and difficult to manager for. For example lake levels in Lake Tumba in the Democratic Republic of Congo (Inogwabini et al., 2006) and Lake Victoria in Kenya (Birkett et al., 1999; Latif et al., 1999) have been attributed to climate variations and may become more variable in the future. In 1997, floods and high rainfall, triggered by an El Nino event in eastern Africa, resulted in a surface rise of 1.7 meters in Lake Victoria and disrupted agricultural production and pastoral systems (Lovett et al., 2005).  While climate change is projected to cause more frequent and intense ENSO events (Wara et al., 2005) impact are not uniform across East Africa. In fact, the same year that the waters were rising in Lake Victoria, El Nino triggered a severe drought in another location in Kenya, significantly decreasing hydro-electric power output, limiting the availability of electricity to East Africans ( Locett et al, 2005). Further, a projected increase in precipitation may also have an effect on hurricanes and storms in the Atlantic. Land sea and  Gray (1992) HAVE FOUND THAT RAINFALL IN THE Sahel is positively correlated with the intensity of hurricanes in the Atlantic Ocean.

Climate change-induced, warming land and sea surface temperatures are projected to cause more frequent and intense hurricanes and tropical storms that inundate coastal areas (IPCC, 2001). These same extreme weather events can lead to decreased precipitation in interior regions, causing increased drought and desertification, subsequently threatening food security. Threats to food security can then lead to widespread migration of human settlements in order to seek better agricultural land, more available water resources, and escape increased exposure to malaria and other diseases. The impacts of climate change also have the potential to disrupt and potentially reverse progress made in improving the socio-economic well-being of East Africans such as infrastructure development, sustainable agriculture, and tourism.

Sea-Level Rise
Sea-level rise along coastal areas where high human populations occur is likely to disrupt economic activities there, such as tourism, mining and fisheries. Sea level rise and resulting coastal erosion is of particular concern coastal Kenya and Tanzania. Warm sea surface temperatures, extreme weather events, and sea-level rise can lead to the destruction of coral reefs, which absorb the energy of ocean swells (IPCC,2001). Coral reef loss is a significant cause of coastal erosion and a major coastal management issue in both Kenya and Tanzania (Magadza, 2000)

Productive mangrove ecosystems along coastal areas serve as a buffer against storm surges by providing protection from erosion and rising tides associated with sea-level rise. However, mangroves are at threat from deforestation, coastal erosion and extreme weather and have been identified as the most vulnerable species to sea-level rise and inundation (IPCC, 2001). Sea-level rise is also threatening the availability of freshwater by causing saltwater intrusion into Tanzania's aquifers and deltas. In the tea-producing regions of Kenya, the world's second-largest exporter of tea, a small temperature increase (1.2C form now) and the resulting changes in precipitation, soil moisture and water irrigation would cause large areas of land that now support tea cultivation to be largely unusable. Economically, this would have far-reaching impacts because tea exports account for roughly 25% of Kenya's export earnings and employ about three million Kenyans (10% of its population) (Simms, 2005).

Biodiversity
Despite Africa's fast-growing human population and the associated impacts on natural resources, it is one of the least studied continents in terms of ecosystem dynamics and climate variability (Hely et al 2006). However, climate change is already having an impact on the dynamics of Africans biomes and its rich biodiversity, although species composition and diversity is expected to change due to individual species response to climate change conditions (Erasmus et al 2002). The projected rapid rise in temperature combined with other stresses, such as the destruction of habitats from land-use change, could easily disrupt the connectedness among species, transforming existing communities, and showing variable movements of species through ecosystems, which could lead to numerous localized extinctions. If some plant species are not able to respond to climate change, the result could be increased vulnerability of ecosystems to natural and anthropogenic disturbance, resulting in species diversity reductions (Malcolm et al, 2002)

Climate change is expected to significantly alter African biodiversity as species struggle to adapt to changing conditions (Lovett et al., 2005).

Historically, climate change has resulted in dramatic shifts in the geographical distributions of species and ecosystems and current rates of migration of species will have to be much higher than rates during post-glacial periods in order for species to adapt (Malcolm et. Al., 2002). Species that have the capability to keep up with climate shifts may survive; other that cannot respond will likely suffer. For example, biome sensitivity assessments in Africa show that deciduous and semi-deciduous closed-canopy forests may be very sensitive to small decreases in the amount of precipitation that plants receive during the growing season, illust5rating that deciduous forests may be more sensitive than grasslands or savannahs to reduced precipitation (Hely et al,.2006). invasive species and other species with high fertility and dispersal capabilities have been shown to be highly adaptive to variable climatic conditions (Malcolm et a.2002). Due to its climate-sensitive native fauna, East Africa may be particularly vulnerable to exotic and invasive species colonization.

Migratory species that use Africa may also be vulnerable to changes in climate. In fact, climate change has the potential to alter migratory routes (and timings) of species that use both seasonal wetlands (e. g., migratory birds) and track seasonal changes in vegetation (e.g., herbivores), which may also increase confects with humans, particularly in areas where rainfall is low (Thirgood et al., 2004). Land-use patterns in Africa can also prevent animals from changing their migratory routes, for example, park boundary fences have been demonstrated to disrupt migratory journeys, leading to a population decline in wildebeest (Whyte and Joubert 1988).

Climate change also threatens some of the large protected areas (including ones that protect migratory species) that have been designated to conserve much of Africa's that magnificent biodiversity. It is expected that vegetation will migrate or move in order to utilize suitable habitats requirements (i.e., water and nutrient availability); however, this may mean that in some locations the geographical range of suitable habitats will shift outside the protected area boundaries. In some locations, the geographical range of suitable habitats will shift outside the protected area boundaries. In addition, weather extremes can also affect biodiversity in more complex says. For example, in African elephants (Loxodonta Africana), breeding is year-round, but dominant males mate in the wet season and subordinate males breed in the dry season. Subsequently, a change in the intensity or duration of the rainy versus drought seasons could change relative breeding rates and, hence, genetic structures in these populations (Poole, 1989; Rubenstein, 1992).  Strategies for future designations of protected areas in East Africa need to be developed that include projections of future climate change and corresponding changes in the geographic range of plant and animal species to ensure adequate protection.

Large changes in ecosystem composition and function because of regional climate change would have cascading effects on species diversity (Sykes and Prentice, 1996; Solomon and Kirilenko, 1997; Kirilenki and Solomon, 1998).  Vast forest disappearance due to climate change-induced die-back and land-use change would substantially affect species composition and global geochemical cycling, particularly the carbon cycle (Malcolm et al.,2002). In the savannahs of Zambia, research shows that climate change substantially affects growth in certain tree species. Chidumayo (2005) showed that dry tropical trees suffer severe water stress at the beginning of the growing season and that a warmer climate may accelerate the depletion of deep-soil water the species depend on for survival. In sub-Saharan Africa, which includes parts of East Africa, several ecosystems, particularly grass and shrub savannahs, are shown to be highly sensitive to short-term availability of water due to climate variability (Vanacker et al., 2005). Shrub and grassland vegetation types generally have root systems that are shallow and dense; these plants draw their moisture from water that is available in upper soil layers and growth in these species depends highly upon the timing, intensity and duration of rainfall. Climate projections suggest that during already dry months, less precipitation will occur likely reducing the resilience of these plants (Vanacker et al.,2005). Changes in plant composition will also have an impact on ecosystem resilience; less diverse systems can be more sensitive to precipitation fluctuations.  For example, ecosystems that are comprised of a uniform herbaceous cover, such as in savannah plant communities, show the highest sensitivity to precipitation fluctuations when compared with plant communities of a mix of herbaceous, shrub and tree species that support a higher diversity of species (Vanacker et al., 2005).

Climate change may also affect species range, which could have profound impacts on species population size. For example in South Africa, a modelling study found that a reduction in the range of a species I likely to have an increased risk in local extinction climate change 9Erasmus et al.,2002). The authors suggest that this may be due to the positive inter-specific relationship between population size and range size; if range size decreases, there is a likelihood that there will be a rapid decline in population size. Additionally, this relationship could be exacerbated if climate change restricts the range of a species to jus a few key sites and an extreme weather event occurs, thus driving up extinction rates even further(Erasmus et al., 2002). Species ranges will probably not shift in cohesive and intact units and are likely to become more fragmented as they sift in response to changing climate (Channel and Lomolino, 2000). In fact, up to 66% of species may be lost due to predicted range shifts caused by climate change in south Africa's Krueger National Park (Erasmus et al., 2002). To be able to better conserve biodiversity in the future, it is imperative to understand how species and ecosystems are likely to change under varying climate change scenarios (Erasmus et al.,2002).

Resistance to Climate
Both short and long term adaptation strategies in response to regional climate change are beginning to emerge in a region that is rife with challenges. For every USD$1 spent preparing for disaster, USD$7 is spent recovering from disaster (Simms, 2005). As organizations test and develop new conservation concepts, it is clear that poverty alleviation must be considered with the conservation of nature and biodiversity. As some resources become scarce, conflicts between conservation and other land uses are likely to increase under climate change scenarios. However, human communities across Africa are banding together cooperatively to conserve resources and protect their livelihood.

Along the Tanzania coast, leading conservation groups are working with natural resource mangers and other stakeholders to integrate climate change adaptation strategies into their management philosophies and plans (Hansen et al., 2003). Initial vulnerability assessments and adaptation planning from Tanzania point to the need for mangrove protection, reforestation with "climate-smart species",  integrated land-use and marine planning, as well as activities to improve resource use technology. Coordinating the testing of adaptation methods in geographically diverse locations within a common habitat type aims to increase the replicability so that the project result can be transferred to other conservation efforts around the globe (Hansen et al.,2003). Conservation of ecosystems and natural resources requires that adaptive management strategies are developed or that we accept that many natural systems will be lost to climate change.

Projects should aim to build the capacity of natural resource managers to assess vulnerability and to adapt management strategies to respond to expected climate change impacts (Hansen et al., 2003).

Climate change impacts to rural farming communities can be reduced by distributing climate data regarding seasonal climate forecasts (based on short-term and long-term forecasts) to small framers so that they can make a more informed farming decision and adapt to the changing climate conditions. Some farmers have already started to use this information and are preparing themselves for dry conditions by planting drought-tolerant crops )Patt et al.,2005).

Food production can be improved dramatically in dry areas when governments and/or organizations use climate forecasts and prepare accordingly by potentially distributing drought-tolerant seeds (Patt et al., 2005). Farmers can also take advantage of climate forecasts by planting less drought-tolerant and higher-yield., long season maize when wetter than usual growing seasons are forecast )Patt et al., 2005). While seasonal forecasts can be useful in some situations, it should be noted that they can not be applied everywhere and that many times they do not consider multiple climate extremes, for example, they may forecast drought but not extreme rainfall. The aforementioned approaches are just a few of the many examples that governments, organizations, and communities need to consider in order to adapt to challenges of subsistence food production and assure future food security (Patt et al., 2005; Ziervogel,2004).

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by admin

The impact of climate change on agriculture

John Quiggin -  Australian Research Council Federation Fellow, School of Economics and School of Political Science and
International Studies, University of Queensland.

It is now virtually certain that Australia and the world will experience significant climate change over the next century, as a result of human-caused emissions of carbon dioxide (CO2) and other greenhouse gases. This note is a brief discussion of the projected effects of climate change on agriculture, under ‘business as usual’ conditions in which global concentrations of CO2 grow steadily and under the assumption that a global mitigation effort successfully stabilises global concentrations of CO2 and slows the climate change. Both global effects and effects on Australian agriculture are considered, with a particular focus on irrigated agriculture in the Murray–Darling Basin.

Comparisons in which the baseline simulation involves no climate change are not particularly useful. A more appropriate basis for analysis is a comparison between ‘business as usual’ and a stabilisation option, in which policy responses ensure that the atmospheric concentration of greenhouse gases is stabilised at a level consistent with moderate eventual climate change. Although the latter definition is somewhat vague, a target of 550 ppm has been proposed on a number of occasions (Stern 2007). For typical estimates of climate sensitivity, this target implies temperature change of around 0.2 degrees per decade over the next century, with stabilization thereafter.

strong>Direct effects of higher temperatureswhile one may be reasonably optimistic about the prospects of adapting the agricultural production system to the early stages of global warming, the distribution of the vulnerability among the regions and people are likely to be uneven. Because losses are concentrated in developing countries, global warming implies a significant increase in the number of people at risk of hunger, although this risk may be mitigated by the expansion of trade. For warming of more than 2 degrees C, the marginal effects of additional warming are unambiguously negative. Studies of wheat yields in mid-to-high latitudes, summarised in Figure 5.2b(c) of IPCC (2007) show that the benefits of warming reach their maximum value for warming of 2 degrees C, while at lower latitudes, and for rice, the effects of warming greater than 2 degrees are clearly negative. For temperature increases of more than 3 degrees C, average impacts are stressful to all crops assessed and to all regions.

Rainfall and evapotranspiration
Water, derived from natural precipitation, from irrigation or from groundwater, is a crucial input to agricultural production. IPCC (2007, Chapter 3, p175) concludes, with high confidence, that the negative effects of climate change on freshwater systems outweigh its benefits. This negative finding arises from a number of features of projected climate change.

First, climate change is likely to exacerbate the spatial variation of precipitation, with average precipitation increasing in high rainfall areas such as the wet tropics, and decreasing in most arid and semi-arid areas (Milly, Dunne and Vecchia 2005). Second, climate change is likely to increase the variability and uncertainty of precipitation (Trenberth et al 2003). The frequency and geographical extent of severe droughts are likely to increase by multiples ranging from two to ten, depending on the measure (Burke, Brown, and Nikolaos 2006) and high intensity rainfall events are likely to become more prevalent (IPCC 2007a). Third, higher temperatures will lead to higher rates of evaporation and evapotranspiration, and therefore to increased demand for water for given levels of crop production (Döll 2002). Water stress (the ratio of irrigation withdrawals to renewable water resources) is likely to increase in many parts of the world. Water stress may be reduced in some areas, but the benefits of increased precipitation will be offset by the fact that the increases in runoff generally occur during high flow (wet) seasons, and may not alleviate dry season problems if this extra water is not stored (Arnell 2004).

Increases in atmospheric concentrations of CO2 will, other things being equal, enhance plant growth through a range of effects including stomatal conductance and transpiration, improved water-use efficiency, higher rates of photosynthesis, and increased light-use efficiency (Drake, Gonzalez-Meler, and Long 1997). However, only modest increases in yields can be expected from increases in CO2 beyond 550 ppm. Temperature and precipitation changes associated with climate change will modify, and often limit, direct CO2 effects on plants. For instance, high temperatures during flowering may lower CO2 effects by reducing grain number, size and quality. Some of these effects may be overcome by appropriate selection of cultivars (Baker, 2004). Increased temperatures may also reduce CO2 effects indirectly, by increasing water demand. Xiao et al. (2005) found that, for given availability of water, the yield of wheat declined for temperature increases greater than 1.5 degrees C. Additional irrigation was needed to counterbalance these negative effects.

strong>Aggregate global impacts
In assessing the aggregate impact of climate change on agriculture it is necessary to take account of the interaction between production systems and markets. In general, demand for agricultural products is inelastic. Conversely, the elasticity of equilibrium prices with respect to exogenous shifts in aggregate supply is typically greater than 1. That is, a reduction in global agricultural output caused by an exogenous shock such as climate change will increase the aggregate revenue of the agricultural sector. This general result must be qualified, however, by the observation that global markets are not frictionless. If, as most projections suggest, moderate warming will increase output in temperate-zone developed countries while reducing output in (mainly tropical) developing countries, the net impact is ambiguous. A number of studies have attempted to estimate the impact of global warming on agricultural output and on aggregate returns to the agricultural sector. Fischer et al. (2002) estimate that, under a ‘business as usual’ projection, global output of cereals will decline by between 0.7 per cent and 2.0 per cent, relative to the case of no change in climate, while the estimated change in agricultural GDP ranges from -1.5 per cent to +2.6 per cent. Darwin (1999) estimates that world welfare may increase if the average surface land temperature does not increase by more than 1.0 or 2.0 C, as is likely under stabilisation If the average surface land temperature increases by 3.0 C or more, however, world welfare may decline. Similarly, Parry, Rosenzweig, and Livermore (2005) find that stabilisation at 550 ppm avoids most of the risk of increased global hunger associated with a ‘business as usual’ projection.

Impact on Australian agriculture- the case of the Murray–Darling Basin
Australian agriculture has always been subject to climatic change and variability. Over the course of the 21st century, climate change arising from human activities will have increasingly significant effects. The effects of climate change will depend both on the extent to which action to mitigate climate change is effective and on the response of global and regional climatic systems. The most detailed analysis of the economic effects of climate change on Australian agriculture is the modelling of effects on irrigated agriculture in the Murray–Darling Basin undertaken by Quiggin et al (2008) for the Garnaut Review. Irrigated agriculture is particularly sensitive to climate change. Relatively modest changes in precipitation and temperature can have substantial effects of inflows of water to river systems and therefore on the availability of water for irrigation. In the the Murray-Darling Basin, effects of this kind arising from the recent prolonged drought are already being observed.

To assess the impact of climate change, with or without global agreement on mitigation, it is necessary to model the responses of farmers and other users of land and water to changes in the availability of water arising from climate change. Particularly in the case of systems like the Murray-Darling Basin where natural variability is high, modelling must take account of uncertainty. Quiggin et al (2008) projected the effects of climate change under a range of scenarios, taking account of resulting changes in patterns of land and water use under uncertainty. Quiggin et al considered a baseline scenario without climate change and two sets of alternative scenarios. The ‘business-as-usual’ scenarios were based on projections in which emissions grow rapidly. The range of variation reflects uncertainty in models of the regional impact of climate change on the Murray-Darling Basin. In the mitigation scenarios, it was assumed that atmospheric concentrations of CO2 and other greenhouse gases are stabilised at levels of 450 or 550 ppm CO2 equivalent. The analysis distinguishes three factors that determine the severity of the impact of climate change. The modelling work here determines the impact climate change may have on rainfall and consequently inflow inflows to the basin. Under ‘business as usual’, both ‘median’ and ‘dry’ scenarios show significant reductions in inflows to the Basin. As shown in Figure I the reductions in inflows projected by 2100 would make irrigated agriculture economically infeasible.

The second factor is the extent to which there is effective international action to mitigate climate change, resulting in stabilisation of atmospheric concentrations of greenhouse gases. The analysis here considers the implications of stabilization at 450 ppm or 550 ppm. As shown in Figure II, most damage can be avoided in the median scenarios with stabilization at 450 ppm. Stabilization at 550 ppm is sufficient to avoid severe damage in the median scenario, and to delay, but not permanently prevent, damage in the dry scenario. No projections were available for the case of stabilization at 450 ppm in a dry scenario, but it appears likely that damage would be reduced substantially relative to the ‘business as usual’ and 550 ppm scenarios.

The final factor is the extent to which land and water users adapt to climate change. The model analysis incorporates optimal adaptation to changing conditions by farmers and other water users, given the constraints under which they operate. These constraints reflect existing institutional arrangements. Other work undertaken by the Group indicates that improved institutional arrangements could increase the economic and social value derived from water use, and improve capacity to adapt to climate change.

In an unmitigated case, irrigation will continue in the Basin in the immediate term. Later in the century, decreasing runoff and increased variation in runoff are likely to limit the Basin’s ability to recharge

storages. By 2030 economic production falls by 12 per cent. By 2050 this loss increases to 49 per cent and, by 2100, 92 per cent has been lost due to climate change. Beyond 2050 fundamental restructuring of the irrigated agriculture industry will be required.

If the world were to achieve ambitious stabilisation of greenhouse gas concentrations to 450 ppm CO2-e by 2100, it is very likely that producers would be able to adjust their production systems with greater efficiency and technological improvement (not modelled) to adapt with little cost to overall economic output from the Basin under this scenario. By 2030 economic production falls by 3 per cent. By 2050, this loss increases to 6 per cent. By 2100, 20 per cent has been lost due to climate change.

Agriculture is the economic activity in which human dependence on natural biological and climatic systems is most direct and fundamental. Unsurprisingly, it is the activity most vulnerable to climate change. The results derived above show that a ‘business as usual’ approach will lead to substantial losses in agricultural productivity, relative to the alternative of mitigation and stabilisation. If human food needs are to be met, this will require the diversion of significant resources into agricultural production. The worst-case scenarios for the Murray–Darling Basin, if repeated globally, would raise the possibility that, even with the substantial diversion of resources into agriculture, it would be difficult or impossible to provide a secure food supply to the world population. The need to rule out such worst-case outcomes is one reason early action on climate change is necessary, even in the absence of a comprehensive international agreement.

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