Biology Reference
In-Depth Information
1948-50 with photos taken in 1999-2000 on the north slope of Alaska,
for example, show substantial expansion of the range of several deciduous
shrubs and white spruce (
Picea glauca
) (Sturm et al. 2001). Even in deserts,
terrestrial ecosystems are responding to global change. In southeastern
Arizona, for example, increased winter rainfall since 1977 is associated
with major increases in shrub density and cover on a long-term study area
(Brown et al. 1997).
Numerous changes in the phenology of plant species appear to result
from these global changes. In parts of the temperate zone, many plants
have shown earlier leafing and flowering in spring (Fitter and Fitter
2002). Some of the best long-term observations of phenological change
for plants come from southern Wisconsin. Leopold and Jones (1947)
compared the timing of seasonal events in 1935-45 with those observed
by William Trelease at a nearby location in 1881-85. In general, spring
events occurred 2 wk earlier in 1935-45 than in the late 1800s. Bradley
et al. (1999) extended the comparison to 1998. Of 55 spring events that
could be compared to those in the 1930s and 1940s, 18 were up to 2 wk
earlier in 1998. Another 20 events showed no significant change, indicat-
ing that relationships involving various components of the ecosystem
were not occurring in parallel.
Te rrestrial animals have also shown changes in seasonal activity pat-
terns. Many migratory birds have appeared earlier in the season in Europe
and North America, although in a few cases migration has been delayed.
Many short-, medium-, and long-distance migrants showed earlier migra-
tion schedules in western Europe, apparently in close response to stronger
influence of the North Atlantic Oscillation (Hüppop and Hüppop 2002).
In New York and Massachusetts, short-distance migrants showed spring
arrival dates averaging 13 days earlier and long-distance migrants 4 days
earlier in 1951-93 compared to 1903-50 (Butler 2003). Changes in com-
munity composition have occurred among land birds (Lemoine and Böh-
ning-Gaese 2003). In the Lake Constance region of central Europe, long-
distance migrant species have declined while short-distance migrants and
resident species have increased in abundance as winter temperatures have
become milder. In California, many butterfly species of the Central Valley
show earlier spring flights, in many cases by more than 3 wk (Forister and
Shapiro 2003). In the United Kingdom, numerous butterflies have
emerged and amphibians have begun to breed earlier in the year (Beebee
2002; Root et al. 2003).
Range shifts by plant and animal species also appear to be resulting
from climatic change. Meta-analysis of long-term studies of geographic
