From the first paragraph, we get the impression that George Marsh [A] cherishes his adolescence memories. [B] thinks highly of the efficiency of agriculture. [C] may not have happy memories of past time. [D] cannot remember his adolescence days.
Anecdotal evidence of a looming Crisis in biodiversity is now being reinforced by science. In their comprehensive surveys of plants, butterflies and birds over the past 20 to 40 years in Britain, ecologists Jeremy Thomas and Carly Stevens found significant population declines in a third of all native species. Butterflies ate the furthest along-71 percent of Britain’s 58 species are shrinking in number, and some, like the large blue and tortoiseshell, are already extinct. In Britain’s grasslands, a key habitat, 20 percent of all animal, plant and insect species are on the path to extinction. There’s hardly a corner of the country’s ecology that isn’t affected by this downward spiral.
The problem would be bad enough if it were merely local, but it’s not: because Britain’s temperate ecology is similar to that in so many other parts of the world, it’s the best microcosm scientists have been able to study in detail. Scientists have sounded alarms about species’ extinction in the past, but always specific to a particular animal or place--whales in the 1980s or the Amazonian rain forests in the 1990s. This time, though, the implications are much wider. The Amazon is a "biodiversity hot spot" with a unique ecology. But in Britain, "the main drivers of change are the same processes responsible for species’ declines worldwide, ’says Thomas. The findings, published in the journal Science, provide the first clear evidence that the world is in the throes of a massive extinction. Thomas and Stevens argue that we are facing a loss of 65 to 95 percent of the world’s species, on the scale of an ice age or the meteorite that may have wiped out the dinosaurs 65 million years ago.
If so, this would be only the sixth time such devastation had occurred in the past 600 million years. The other five were associated with one-off events like the ice ages, a volcanic eruption or a meteor. This time, ecosystems are dying a thousand deaths--from overfishing and the razing of the rain forests, but also from advances in agriculture. The British study, for instance, finds that one of the biggest problems is nitrogen pollution. Nitrogefi is released when fossil fuels burn in cars and power plants-but also when ecologically rich heath-lands are plowed and fertilizers are spread. Nitrogen-rich fertilizers fuel the growth of tall grasses, which in turn overshadow and kill off delicate flowers like harebells and eyebrights.
Even seemingly innocuous practices are responsible for vast ecological damage. When British farmers stopped feeding horses and cattle with hay and switched to silage, a kind of preserved short grass, they eliminated a favorite nesting spot of corncrakes, birds known for their raspy nightly mating calls; corncrake populations have fallen 76 percent in the past 20 years. The depressing list goes on and on.
Many of these practices are being repeated throughout the world, in one form or another, which is why scientists believe that the British study has global implications. Wildlife is getting blander. "We don’t know which species are essential to the web of life so we’re taking a massive risk by eliminating any of them, " say’s David Wedin, professor of ecology at the University of Nebraska. Chances are we’ll be seeing the results of this experiment before too long.