In Chapter 5 of Rambunctious Gardens, Marris introduces assisted migration to us. Anthropogenic climate change, caused by human emissions of gases, “is the biggest single thumbprint humans have put on this planet” (74). Therefore, species are expected to (and have already began to) move, as they cannot handle the escalating temperatures. Marris defines assisted migration as human intervention in helping species respond to climate change. Previously, species would “move around slowly, in geological timescales,” (80) but anthropogenic change is much more rapid that assistance is necessary.
To put this into perspective, Camille Parmesan “estimated that the average species’s range…moves 3.8 miles toward the pole every decade…spring events are occurring 2.3 days earlier per decade” (76-77). Assisted migration is an answer to prevention of early extinction, particularly the mountain species, such as the introductory example of the American pika. The Puth and Burns article on New York’s Nature may be an indication of this, presenting that 65% of long-term records “documented declines in species richness; this percentage rose to 77% when only studies describing native species were included.” The cause of this, as postulated by authors of the records, were a variety of “mainly anthropogenic causes, including development, exotic species, changes in land use, chemical contamination and recreational use of natural areas” (16). Several authors provided the following general rules for assisted migration: at a high risk of extinction, can be feasibly transported, and if the benefits outweigh the costs.
Two of the main arguments against assisted migration are the possibility of the organism dying or becoming invasive. In Marris’ words, “What is interesting about climate change is that it pits two common assumptions against each other: the pristineness myth and the myth of a correct baseline for each area” (77). As stated, the main argument for assisted migration is preventing early extinction. “Opponents are more worried about the integrity of coevolved ecosystems” (78). As is the problem with rewilding, the outcomes can be very unpredictable. Moving a single species can disrupt an entire ecosystem, as species rely on each other. The example that Marris provides begins with butterflies: they can move easily across a landscape, but they only lay their egg specific plants, which depend on insect or bird pollinators. Problems arise when pollinators migrate before the plant species, who may be “too slow to outrun climate change” (76), can. In other words, “though one species may be going extinct, the measures that could save it might endanger other ecosystems, might threaten the existence of the baselines that guide conservation efforts, and might piss off other conservationists” (81).
As with my stance on rewilding, I feel that the concept of assisted migration is a romantic one at most. I am not a firm believer in the future of it because of the unpredictable and possible negativities. I understand the reasoning behind why there are supporters who advocate for it. However, I am very much against assisting migration for commercial purposes rather than for nature’s sake. Further, there is a very selective group of species that assisted migration would work for, making it selective. That still leaves many other species vulnerable to extinction left behind.
