Effects of Global Warming: Agriculture, Plants and Animals

    AGRICULTURE

   Global warming of a few degrees may increase agricultural production, but not necessarily in the same places where crops are grown now. Southern Canada, for example, may benefit from more rainfall and a longer growing season. At the same time, the semiarid tropical farmlands in some parts of Africa may become further impoverished. Farming regions such as California’s Central Valley that bring in irrigation water from distant mountains may suffer as the winter snowpack, which functions as a natural reservoir, melts before the peak growing months. Crops and woodlands may also be afflicted by more insects and plant diseases. Agricultural areas will need to adapt to changing conditions, such as by shifting the types of crops grown or investing in drought-tolerant or heat-tolerant varieties. Scientists estimate that warming of up to about 3 Celsius degrees (5.4 Fahrenheit degrees) could increase global agricultural potential, but that further warming is likely to decrease this potential.

 PLANTS AND ANIMALS

   Plants and animals will find it difficult to escape from or adjust to the effects of global warming. Scientists have already observed shifts in the lifecycles of many plants and animals, such as flowers blooming earlier and birds hatching earlier in the spring. Many species have begun shifting where they live or their annual migration patterns due to warmer temperatures.

   With further warming, animals will tend to migrate toward the poles and up mountainsides toward higher elevations. Plants will also attempt to shift their ranges, seeking new areas as old habitats grow too warm. In many places, however, human development will prevent these shifts. Species that find cities or farmland blocking their way north or south may become extinct. Species living in unique ecosystems, such as those found in polar and mountaintop regions, are especially at risk because migration to new habitats is not possible. For example, polar bears and marine mammals in the Arctic are already threatened by dwindling sea ice but have nowhere farther north to go.

  Projecting species extinction due to global warming is extremely difficult. Some scientists have estimated that 20 to 50 percent of species could be committed to extinction with 2 to 3 Celsius degrees (3.6 to 5.4 Fahrenheit degrees) of further warming. The rate of warming, not just the magnitude, is extremely important for plants and animals. Some species and even entire ecosystems, such as certain types of forest, may not be able to adjust quickly enough and may disappear.

    Ocean ecosystems, especially fragile ones like coral reefs, will also be affected by global warming. Warmer ocean temperatures can cause coral to “bleach,” a state which if prolonged will lead to the death of the coral. Scientists estimate that even 1 Celsius degree (1.8 Fahrenheit degrees) of additional warming could lead to widespread bleaching and death of coral reefs around the world. Also, increasing carbon dioxide in the atmosphere enters the ocean and increases the acidity of ocean waters. This acidification further stresses ocean ecosystems.