A productive, but taxed, Earth
A UN-sponsored study finds that humans' growing demands have damaged the planet at unprecedented levels.
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The loss of coral, for instance, is often attributed to degraded coastal waters that were harmed over time. Mangrove swamps that filter pollutants were bulldozed for apartment buildings. Combine that with large human populations living seaside and increased agricultural runoff flowing into the oceans. Now add overharvesting of fish that eat algae. Suddenly, you've got algae blooms that overwhelm coral reefs, Dr. Agardy says.Skip to next paragraph
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It's not known what changes have kept the cod from rebounding. Some say a change in ocean salinity. Others, including former fishermen, have blamed seals for eating them. Harp seal pups were butchered on the ice this spring for their pelts, but also in the expectation that a smaller seal population would help the cod recover.
But in years past, the cod recovered even with seal predators present, Agardy says. "It's pretty clear that cod have been fished down to a point where it will be hard for them to ever recover," she adds.
Yet changes in fishing policy and enforcement of those changes may help oceans recover, she says, adding that the question now is whether the political will exists to create change.
A key element of the UN report was to bring together economists and biologists to examine the impact of ecosystem changes on human well-being. In accounting terms, the report says, the loss of an ecosystem can be equated to loss of a capital asset.
For instance, exploitation of nature has benefited the economies of nations like Ecuador, Kazakhstan, Democratic Republic of Congo, and Venezuela. But those nations actually experienced a "loss in net savings" when depletion of natural resources (energy and forests) and damage from carbon emissions were factored in, the report found.
A key finding was that abrupt, unexpected changes in ecosystems are increasingly likely. Changes are usually gradual in ecosystems, yet once a threshold is crossed, stark and rapid changes are possible.
Susan Minnemeyer spotted one of those changes a few years ago while peering for the first time at sharp satellite photos of Cameroon's dense tropical rain forest. As global information systems manager for Global Forest Watch project at the World Resources Institute in Washington, she noticed tiny lines in the forest, a spider's web criss-crossing the jungle - thousands of miles of illegal logging roads.
Losing valuable forest to illegal logging is bad enough, she notes, but another critical hidden cost has emerged: loss of wildlife.
Superficially, the Cameroon forest looks intact even after such logging because the forests aren't clear-cut; just the valuable trees are taken. But the illegal roads have opened up paths for hunters.
The growth of the bushmeat trade is rapidly depopulating the forests of all large mammals, Ms. Minnemeyer says. Her finding was just one of many examples of accelerating species loss cited in the study.
"It can look intact from the sky," Ms. Minnemeyer says. "But this is an empty forest - it's actually devoid of wildlife. We think we can change this, and we're working with the government to do that."