Biology Reference
In-Depth Information
southern oceans (Thompson and Solomon 2002). The chemistry of the
earth's air, waters, and soils has thus been altered in many ways.
In terrestrial ecosystems, global climate change is expressed as altered
annual regimes of temperature and precipitation, longer growing seasons
at high latitudes, reduced snow cover at high latitudes and altitudes,
reduced cloud cover in the humid tropics, and increasing incidence of
severe weather events. Patterns of change are complex, however, and
major regional differences exist in the magnitude and direction of
changes. Nevertheless, several general patterns are evident. Satellite data
show that the growing season at latitudes between 45° and 70°N has
lengthened by about 18 days in Eurasia and 12 days in North America
over the past 20 yr (Peñuelas and Filella 2001; Lucht et al. 2002). Terres-
trial snow and ice cover has declined about 10% since 1960. These
changes translate into an increase of about 6% in total terrestrial net pri-
mary production between 1980 and 2000 (Nemani et al. 2003). Ecosys-
tems in the humid tropics and higher latitudes of the northern hemi-
sphere showed the greatest increases.
Freshwater ecosystems, especially at higher latitudes, are also begin-
ning to experience altered seasonal temperature regimes (Schindler
1988). The ice-free season is lengthening, water levels are dropping, the
surface water temperatures are increasing, and the thermocline is deepen-
ing. Surface water inflows are likely to decrease, together with inflow of
dissolved materials.Acid deposition and increased ultraviolet radiation are
additional impacts of particular importance in freshwaters.
Marine ecosystems are experiencing global change. In the southern
oceans, both surface and subsurface waters to a depth of 1,100 meters
have warmed significantly over the past 50 yr (Gille 2002). In tropical
oceans, surface waters have warmed by about 1-2°C over the past cen-
tury.Thermal expansion of warmed surface water, together with melting
land and sea ice, is leading to rising sea level. In the North Atlantic, release
of freshwater by melting of sea ice and terrestrial ice caps may alter ocean
currents that bring warm water to the coast of northwestern Europe
(Stevens 1999). In the Pacific Ocean, oceanic circulation and water tem-
perature changes beginning in the mid-1970s have affected major oceanic
regions both north and south of the equator (Hayward 1997). In the Cal-
ifornia Current, for example, warmer water has been associated with a
large decline in zooplankton and seabirds (Veit et al. 1997).
From the arctic to the tropics, climatic change has already affected the
distribution and phenology of many species and communities (Peñuelas
et al. 2002; Walther et al. 2002). Comparison of aerial photos taken in
