The group's predictions appear to be backed by evidence in the wild. When wolves from the Canadian wilderness were reintroduced into Yellowstone in 1995 and 1996, the local coyote population halved within two years. The wolves hunted and killed their smaller rivals. The researchers also found that once a species dies out, many others follow in a cascade of extinctions. The larger the number of species in the original com- munity, the greater the effect.
Plants also appear to be at risk from a cascade of extinctions.
For instance, studies have shown that Middlesex Fells, an isolated 400-hectare woodland park in Boston, Massachusetts, lost nearly 40 per cent of its original species between 1894 and 1993. Wherever we have the data to look carefully at plant communities, we are seeing a massive loss of species. In many cases we don't understand it. Waller says that preserving existing species may be more cost-effective than trying to reintroduce lost ones. Captive breeding, habitat restoration, and reintroduction are intensive and expensive.