Environmental Engineering Reference
In-Depth Information
Such
Homo sapiens
-loving species adapt to city dwelling in interesting ways. Gray squirrels get
more aggressive and daring. Many birds sing louder and move up the scale, singing higher notes that
are less likely to be drowned out by the rumble of city traffic.
22
Pigeons make what appear to be regular
planned journeys on the London Underground, saving their wings and energy as they commute to get to
food supplies or return to their nests.
23
In many postindustrial landscapes, including places such as Milwaukee, there are movements to
“green” cities by putting nature onto former industrial sites. But too often the emphasis is on creating
sanitized, planned green spaces rather than sitting back to see what emerges. Studying the urban wildlife
that nature itself throws up has long been a backwater of ecology, but a new generation of researchers is
catching up, with resources like the
Nature of Cities
blog, founded by New York environmental scientist
David Maddox.
24
Britain's University of Bristol has set up an urban pollinators project, tracking down
urban wildflower meadows.
25
But many governments are hostile. They see cities as hotbeds of alien in-
vasions, disreputable ecosystems, and species that just shouldn't be there. The European Union, which
has passed new legislation to force governments to act against aliens, reported in 2013 that invasive spe-
cies “threaten urban environments.” It never quite explained why.
26
The International Union for the Conservation of Nature (IUCN) published its own study of “invasive
alien species” in urban Europe, highlighting the presence of American bullfrogs and Canada geese in
Flanders, rabbits in Helsinki, hogweed in Estonia, New Zealand flatworms in Scotland, the raccoon in
Berlin, the Hottentot fig in Dublin, and Indian parakeets in London. The charges included spreading
disease, damaging monuments, and triggering allergic reactions.
27
They also “take over resources and
space from the indigenous species,” said Chantal van Ham, the IUCN's European program officer.
28
But
do they? Or do they expand biodiversity and create opportunities for others?
Urban parks and gardens are increasingly valuable spaces for wildlife of all sorts. In Britain, do-
mestic back gardens cover up to a quarter of most urban areas. A study found 70 percent of their flora
parks are similarly planted with foreign as well as domestic plants, leading James Gagliardi, a horticul-
turist with Smithsonian Gardens, a division of the Smithsonian Institution, to describe the incomers as
“bullies that crowd out native plants and damage the diverse ecosystems that many living things depend
on.” But often this lively mix of natives and aliens
are
the urban environment. According to the British
government agency Natural England, urban gardens, even if dominated by aliens, are vital habitats for
many native species, from the common frog and the song thrush to the hedgehog.
30
Transportation links can be equally important novel ecosystems for wildlife. Railway routes have
been valuable ways for alien species and others to move around. Highways, too. Conservationists usu-
ally see roads as barriers to migrating wildlife, because they fragment the landscape into small pieces
and can trap the unwary. But highway easements can also be migration corridors. In the 1980s, the Brit-
ish government successfully recruited the easement on the highway between London and Oxford to link
two protected woodlands. Invertebrates such as butterflies could not make the journey using the sur-
rounding countryside because the fields were full of agricultural chemicals. So wildflowers and black-
thorn bushes were seeded beside the roaring traffic. The plan worked, and twenty-five butterfly species,
including the rare black hairstreak, duly colonized.
31
Europe's most remarkable brownfield site—an area the size of Luxembourg—is the exclusion zone
around the stricken Chernobyl nuclear reactor in Ukraine. With humans banished since the catastrophic
Search WWH ::
Custom Search