Possible Impacts on Ecosystems and Extreme Events

Tire complexity of the climatic system makes any prediction difficult, and there is room for uncertainty. However, recent changes can already be attributed to global warming, and scientists can predict for some regions what types of impacts are more likely to happen over time. In recent years temperature and precipitation patterns have been commonly reported in the news.

Tire IFCC has already predicted that floods, fires, and heat waves can be more frequent. Regions such as sub-Saharan Africa, South America, and Southeast Asia can experience increased heat and thus a decline in subsistence agriculture, leading to desertification. Grasslands of North America and Africa may initially have positive impacts from global warming as the photosynthetic rate increases. But unpredictable climatic conditions can reduce crop production in important agricultural regions.

Forests of northern latitudes seem to have already benefited from global warming. Warmer temperatures may extend the optimal growing conditions of North American forests farther north. A shorter ice period and the decay of permafrost may drastically change the lives of migrating animals and nomadic human populations of the Arctic.

With longer growing seasons and increased temperatures, several species of animals and plants will be forced to migrate or respond through adaptations to new conditions. For some species, such as birds, migration is a highly probable response, whereas the migration rate for most plants may be too slow, and adaptive responses are the only means of survival to new environmental conditions.

For several species, with habitat loss and the existence of human settlements, migration will not be an option. In the oceans, changes in temperatures can bring variations in sea current patterns and a change in the distribution of many species of fish. In both aquatic and terrestrial ecosystems, these potential changes in species can have huge impacts on global biodiversity and rate of extinction.

Another major change may be a rise in ocean levels. Estimates of the increase in sea level range from 1 to 10 centimeters per decade during the next century as polar ice continues to melt in the warmer climate. Experts do not know if these rates are real, but the rates may have disastrous consequences. Because a large number of people live along the world's coastlines, the number of environmental refugees could reach millions of people per year during the next century.

It is unclear where all these refugees will go. This is a major concern for the Caribbean islands. Trinidad and Tobago, for example, have already examined the possibilities and have started developing strategies for possible environmental refugees.

Similarly, impacts on human health can be severe. With habitat loss, deaths, starvation, and infectious diseases have been predicted, especially in developing countries, where mitigation and adaptation measures have not yet been developed. Displacement of refugees can degenerate into conflicts for new arable lands. Under such degraded conditions, as is the case in several countries, cases of infectious diseases (such as cholera, typhoid, and malaria) can explode due to lack of hygiene and poor living conditions.

Northward spread of many infectious diseases currently limited to subtropical and tropical regions can occur under higher temperatures. In recent years diseases such as dengue fever have been reported in northern areas where they had never been or had been previously eliminated. This is also the ease for malaria, which reappeared north and south of the tropics.

In urban areas, human health can be of greater concern. Heat strokes have been more frequently reported in the past few years. For example, in 1995 Chicago experienced a heat wave so severe that more than seven hundred heat-related deaths were reported in the metropolitan area alone.

Although it is unclear if that heat wave was related directly to global warming, similar scenarios can be more frequently predicted around the world. In urban centers, with increased temperatures, additional problems such as intensification of ground-level ozone smog will arise, leading to more asthma and other respiratory problems.

Extreme weather events (e.g., hurricanes, storms, droughts, etc.) associated with global warming can harm human health directly and indirectly. A recent report on the state of the environment suggested that with climate change, the coasts of the Gulf of Maine could be more prone to extreme weather events, especially hurricanes and storms.

The number of deaths can increase during such events in areas where ecosystems have been so degraded that they are vulnerable to any type of disturbance. Hurricane Mitch in Central America in 1998 is a good example of an extreme event that had a huge impact on regions with degraded ecosystems. In that case, more than ten thousand people were killed due to mudslides on deforested hillsides. Under such conditions, the impact con be amplified.