In December 2009, scientists reported that the possum is missing from its only home in the mountain forests of northern Queensland, Australia. It hasn’t been seen there in three years. A slight temperature rise (of only 1 or 2 degrees) is likely the reason: The possum typically dies in as few as four or five hours at 86 degrees Fahrenheit.
Researchers, such as Dr. Chris Thomas of the University of Leeds in England, now believe that even under mid-range global-warming scenarios, 15 to 37 percent of our terrestrial species could become extinct by 2050. And that’s just the threat from climate change, without taking into account the added dangers of habitat loss and the migration barriers posed by cities and highways.
“Desperate times call for desperate measures,” or so the proverb goes. That’s why many nature enthusiasts are refusing to wait for the slow wheels of government to turn and are instead participating in an activity called “assisted migration.”
“Assisted migration” is defined as “the practice of deliberately moving members of a species from their present habitat to a new region with the intent of establishing a permanent presence there.” Usually, assisted migration projects are conducted in response to the destruction of natural habitats caused by human actions: most notably, climate change.
In past episodes of global warming, many plants were able to keep up, moving in concert with the changes. But the speed of climate change today is unprecedented in the fossil record. The vast majority of our plants have not evolved for rapid locomotion. Last year, a study published in the science journal Nature predicted that climates would shift, on average, about a 1/3 of a mile per year in the 21st century. It will be fastest — about 3/4 of a mile per year — over flat areas, such as deserts, mangrove swamps and marshes. And it could be as much as 6 miles per year in extreme situations. Without human help, some say, countless species will die.
For example, one group of concerned citizens, the Torreya Guardians, moved 31 seedlings of the endangered Florida torreya, a conifer tree, 400 miles north of its current natural range in Florida to two sites in the North Carolina mountains. In Los Angeles, fans of the quino checkerspot butterfly — a tiny brown, red and black insect that doesn’t like it too hot and dry — carried a few cocoons north beyond the city and into the mountains. The hope is that these species will re-establish themselves in their new habitats.
In most cases of assisted migration, people act on their own without much paperwork or bureaucracy. And for some, that’s the problem.
Slower is better
Many conservation biologists argue that assisted migration is not helping to save the world’s biodiversity; in fact, quite the contrary. By taking the fate of rare and vulnerable species into their own hands, citizen activists are inadvertently harming them at a time when invasive, nonnative plants and animals pose one of the gravest threats to natural areas.
Instead, say those who oppose assisted migration, people should work under the supervision of botanic gardens and government agencies, which are approaching assisted migration cautiously and methodically. Some gardens are now collecting seeds of threatened plants for use in future reintroduction efforts. In order to preserve a species’ genetic diversity, these entities are careful to include samples from a wide variety of populations. Government agencies, they say, have been moving more vigorously to purchase lands in order to create “migration corridors,” large continuous tracts that enable plants and animals to successfully rearrange themselves. And both have been redoubling their efforts to control invasive species.
In the Midwest, where I live, the Chicago Botanic Garden is beginning to test the feasibility of assisted migration for the threatened (federal and state) dune thistle. This imperiled wildflower with puffy, cream to pinkish-tan summer blossoms and blue-green leaves has been driven by development and drought from much of its habitat along the western Great Lakes. In recent years, the garden has been collecting seeds from different parts of the dune thistle’s range and using growth chambers in labs and special germination tables to test the plant’s response to different conditions — and thus to help choose the best places to relocate it in the wild. But those kinds of determinations are still five years away.
Eco-vigilantes or species-saviors?
Those who believe in assisted migration, however, say that “potted” plants are the botanical equivalent of “caged” fauna. Cultivated plants could be far different from their counterparts in the wild if they were propagated from stock at commercial nurseries that have long been in cultivation. Such plants may have adapted to the “easy life,” including regular watering and a lack of competition from other plants and animals.
If a species is getting close to extinction, do you think it’s OK to help it move to a better habitat, or would it be wiser to wait and hope that biologists will save its last representatives?
As climate change intensifies, it’s likely that public monies and scientific manpower will be stretched to the limit just managing species that play major ecological roles. The fate of many non-keystone plants and animals may depend on a few friends willing to help them move — people like you and me.
Feature photo: Climate shift will be fastest over flat areas, such as marshes. ©John T. Andrews.