by Rick Ridgeway
Heart of Winter 2008
For many wild animals, to roam means to survive. Seasonal migration between habitats is a pattern passed from generation to generation of eagles, waterfowl, elk and hundreds of other species. To locate a new place to survive and breed, the young of many species must roam far and wide. And freedom to roam often determines whether or not wild creatures can adapt to change. Even for species that do not seasonally migrate, the ability to find new mates in new places protects genetic health and diversity.
What happens when habitats are isolated by cities and highways, or fragmented by fences and fields? Since the 1960s, conservation biologists have been able to measure with increasing accuracy the minimum sizes of protected areas needed to ensure the long-term survival of all the species in a given ecozone. No surprise: Big animals need big spaces. If territories are balkanized by highways, energy development and housing, the long-term survival of large mammals – as well as the multitude of smaller creatures connected to them – is jeopardized. Imagine it this way: As writer David Quammen has noted, if you cut a beautiful, handwoven Turkish rug into 36 pieces, you don’t end up with 36 Turkish rugs. You have instead 36 worthless remnants.
That’s the first problem. The second one has come into focus only in the last few years: What happens when habitats change because of global warming? What happens when species are marooned in isolated islands of shifting habitat? Many of us followed last year’s reports from the Intergovernmental Panel on Climate Change – the most exhaustive and authoritative studies to date on the likely effects of global warming. If animals remain trapped in their habitats, the IPCC predicted, one-quarter of the earth’s plants and animals could disappear by the end of this century. Nothing like that has happened on this planet since the extinction of the dinosaurs 65 million years ago. It can be argued convincingly that nothing of this magnitude has challenged our own species in our relatively short history on this planet.