The anthropogenic biosphere calls for a new perspective on preserving nature. In his paper for the centennial of the Ecological Society of America, Erle Ellis argues that in order to sustain humanity, we will need to change the way that we view conservation from the historical perspective of conserving and restoring to a new perspective of guiding and re-designing. As one example of how we will need to adjust, he suggests that some species and ecosystems will need to be moved as their habitats shift to northern latitudes. While I agree that our practice of conservation will need to change, the call to move species into new locations places very complicated decisions into the hands of policy makers and managers who have seen firsthand the legacy of this approach from past attempts. The reality of accomplishing conservation through assisted colonization has as much to do with how conservation priorities are ethically perceived and legally set as with our understanding of how a species will adapt to a new location.
Most people are familiar with at least one species that has been moved, intentionally or not, to a new location where it exhibits ‘weed like’ behavior. These invasive species can permanently alter ecosystems by changing community composition, predator/prey relationships, and biogeochemical cycling among other processes. Some invasive species were purposefully moved, such as the European starling brought to New York Central Park in the 1890s to fill the park with the sounds of Shakespeare, or the various species of Asian carp imported into the SE United States in the 1950s to clean commercial ponds, or the cane toad brought to Australia in 1935 to control pest beetle populations. There are literally thousands of stories like these and an international registry, the Global Invasive Species Database of the International Union for Conservation of Nature, that attempts to track their location, ecology, and transport vectors. A quick perusal through the database makes it fairly clear that we don’t understand why some species become invasive. Despite decades of research on the invasion process, we have yet to define what triggers a species to propagate and take over in a new location. In fact, this lack of consistent rules has led to a call for dissolving the field of invasion biology into other ecological fields (Valéry et al. 2013). While invasive behavior is not likely to occur when a rare endemic species is transported because it is facing extinction in its native range, the act of purposefully transplanting species raises many of the same questions and concerns for wildlife managers, politicians, and the public. What is clear is that humans have moved other species going back a long, long time. In this respect, Ellis is right that there is no going back to a nature untouched by us.
There have been success stories with assisted colonization, but the outcomes vary by ecosystem and by the form of legal protection afforded the species. As an example, freshwater species living in flowing waters are among the hardest to conserve or relocate because they exist in linear systems that only extend so many miles upstream. There has been mixed success transplanting freshwater mussels and greater success with some trout species. Yet, habitat modeling into 2080 suggests that there won’t be many places left to transport some cold water species in coming decades (Wenger et al. 2011). Take the bull trout, which exists in very little of its historical habitat within the U.S. and is listed as threatened under the U.S. Endangered Species Act. Researchers are working to transplant some genetically distinct remaining populations into higher elevation lakes where temperatures are cooler and fewer non-native competitors exist. The validity of this assisted migration as a long-term conservation tool remains to be seen. These conservation actions and others are outlined in the interstate Bull Trout Recovery Plan mandated by the species’ listed status. In this particular case, a new more intensive recovery plan was recently drafted as part of a settlement to a lawsuit claiming that the bull trout was not receiving the level of protection authorized by the law. In the U.S., this is one of the few ways that a species can become a priority for conservation action. As you can imagine, the legal system for conservation prioritization varies considerably in other countries.
In a future where restoration and conservation of everything will likely not be possible, conservation priorities will have to be set (Wiens and Hobbs 2015). Moving ahead to a time when the existence of many more species will be threatened by globalization, who will decide what species and habitats are a priority? Some suggest it will be a question of what provides the greatest outcome, a cost-benefit analysis of ecosystem services provided.
One of Ellis’ main tenets in ‘Ecology in an Anthropogenic Biosphere’ is to ask how there is so much diversity in culture/nature relationships. A major challenge moving forward with conservation in the Anthropocene will be reconciling the diversity of these relationships and making conservation decisions that reflect their ecological, social, political, economic, and ethical perspectives.