Geography Reference
In-Depth Information
In subirdia, new ecological interactions such as the renewed competition
imposed on fairy-wrens by noisy miners are precursors to inevitable evolu-
tionary change. Adaptation, an adjustment to new situations such as the pres-
ence of an aggressor, is a creative evolutionary response that gave us the
wonderful diversity of birds that today coexist in shrubby eucalypt wood-
lands. Extinction is also an evolutionary response to new situations, and it is
down this path that many Australian scientists believe the miner is taking
woodland-dependent songbirds. Restoration of native shrubs in suburbs is
proposed as a strategy to exorcise the ghosts of competition before they extin-
guish the fairy-wren and others.
Bewick's wrens and noisy miners tell me that subirdia's diversity is a
work in progress, a melting pot of sorts that brings together animals from
many formerly distinct walks of life. Some of their dif erences evolved in the
past when their ancestors competed. Our actions are bringing some back
into the competitive ring. By opening forests or planting trees in grasslands
and deserts, we bring together in suburbs species from open lands and those
more typically found in forests. Whenever new species come into competi-
tion, we can expect the larger or more aggressive species to exclude the meek
and weak. Almost certainly this exclusion will reduce diversity. Setting aside
refuges and restoring habitat features that allow competitors to coexist are
simple ways to keep subirdia diverse. By keeping dif erent suburbs distinct,
we can also allow species with unique requirements to live somewhat isolated
from each other. For example, in central Bohemia, Czech Republic, black
redstarts prefer open, densely built parts of the city, while redstarts prefer
places with more trees. Black redstarts dominate redstarts, but this is rare
because of the mosaic nature of open and tree-covered habitats in the city.
Keeping open and forested neighborhoods distinct and separate allows cities
in Bohemia, such as Breznice, to host two, rather than a single, species of
redstart.
