A recent study suggests that, because carbon dioxide levels in the atmosphere are rising through the burning of fossil fuels, plants do not need to keep their stomata as wide open as they used to obtain the carbon dioxide they need. As consequence plants are now releasing less water into the atmosphere than they did in the past (Gedney et al., 2006; Matthews, 2006). This represents a very subtle consequence of climate change that affects the global water cycle and makes the important point that the global ecosystem is very complex and that a change in one component can have wide-ranging and unexpected consequences.
In countries like Chad, Afghanistan and Ethiopia, the water crisis is a major problem. For instance, in Chad, 30 million people in the region compete over water. The drying up of the lake has led to migration and conflicts, according to FAO. Fish production has recorded a 60 per cent decline, while pasturelands have been degraded, resulting in a shortage of animal feed, livestock, and biodiversity. The lake’s receding shoreline has severely affected people living in its basin and has turned them into food-insecure refugees.
The availability of freshwater will be significantly altered in a future world affected by climate change (Houghton, 2004). In some regions, water availability will decrease; in others, it will increase. Precise predictions about the extent and exact location of such changes cannot be made because they are based on climate models, the accuracy of which is uncertain. However, there is wide agreement that probable changes will include:
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- More rain in northern high latitudes in winter and in the monsoon regions of south-east Asia in summer.
- Less rain in southern Europe, Central America, southern Africa, and Australia in summer.
- Greater water flows in rivers that are fed by glaciers.
- Overall, higher temperatures in all regions, which will lead to greater evaporation so that, even in regions where rainfall does not decrease, water availability will be reduced.
- Rising sea levels, which will lead to flooding of low-lying coastal regions, including major flood plains and river deltas, many of which are currently densely populated; for example, the Bengal delta in Bangladesh contains 8.5 million people