the edges (Figure17.38). Permafrost is melting, causing swamps in locations that were once
frozen solid. Melting ice caps add water to the oceans, so sea level is rising (Figure17.39).
Also contributing to sea level rise is that water slightly expands as it warms — this expansion
of water accounts for about one-quarter to one-half of the observed sea level change. Since
warmer air can hold more moisture, storms are becoming more intense. Weather is therefore
likely to be more severe with more heat waves and droughts. More rainfall sometimes results
in increased flooding.
Figure 17.38: Sea level has been rising in recent decades. Twenty-three different geologically
stable tide gauge sites with long-term records are represented here. ( 27 )
Plants and animals are feeling the effects of the changing climate. Winters are shorter so
some animals are changing their seasonal behaviors: migrating earlier in the spring, for
example. Coral reefs are dying worldwide due in part to the increase in surface ocean
temperatures. Forests are also dying in some places because warm weather has allowed
insect pests to expand their ranges into areas that were once too cold. As surface seas warm,
phytoplankton productivity has decreased. Some regions that were already marginal for
agriculture are no longer farmable, because they have become too warm or dry.
As greenhouse gases increase, changes will be more extreme. Oceans will become slightly
more acidic, making it more difficult for creatures with carbonate shells to grow, including
coral reefs. A studying monitoring ocean acidity in the Pacific Northwest found ocean acidity
increasing ten times faster than expected and 10 to 20 percent of shellfish (mussels) replaced
by acid tolerant algae.
Plant and animal species seeking cooler temperatures will need to move poleward 100 to
150 km (60 to 90 miles) or upward 150 m (500 feet) for each 1.0°C (8°F) rise in global
temperature. There will be a tremendous loss of biodiversity because forest species can’t
migrate that rapidly. Even if they could, human development would block their spread