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International Policy Guidance for Assisted Colonization of Species Needed

Torreya taxifolia
Florida's "stinking cedar" is one species undergoing assisted colonization. | Malcom Manners/ Flickr

Earth's climate is rapidly changing, leaving species worldwide with an increased risk of extinction. Plants and animals that cannot adapt may need to migrate beyond their historical range to new regions or ecological zones for survival. However, these diasporas are difficult — if not impossible — for many species to make on their own, stymied by human infrastructure and disturbance.

In a Policy Forum in the April 30 issue of Science, researchers argue that global policy guidance for the assisted colonization of species threatened by climate change is urgently needed.

"Assisted colonization could be a critical tool in our toolbox for ameliorating the impacts of climate change on biodiversity, but it could also be dangerous if done wrong," said lead author Jedediah Brodie, an ecologist at the University of Montana. "We argue that the international community needs a clear and coherent framework by which assisted colonization projects can be evaluated, vetted, regulated and reported."

Considering the current negotiations in advance of the meeting of the Conference of the Parties to the Convention on Biological Diversity in October 2021 — an event that will set the course of international conservation policy for many years to come — now is the time to set global standards and targets for assisted colonization, the researchers say.

Assisted colonization, or the translocation and establishment of populations of organisms outside their historical range for conservation purposes, could help some at-risk species escape their shrinking traditional habitats and establish populations in new locations.

According to Brodie, the strategy is becoming increasingly important as the impacts of climate change become increasingly severe. However, despite having been a topic of discussion among conservation scientists for decades, assisted colonization remains a controversial conservation strategy and is often precluded by contradictory global policy.

One of the main arguments against using assisted colonization is fears that translocated species would become invasive and cause irreversible damage to their newly introduced communities. This is a valid concern given humans' poor track record with invasive species thus far, said Brodie.

But this hasn't stopped private citizen groups from acting on their own accord to implement assisted-colonization projects for species without guidance, oversight, or reporting. For example, over the last several years, a group of well-intentioned citizen scientists have been working to translocate the highly-threatened, Florida-native conifer species, Torreya taxifolia or "stinking cedar," to forests in North Carolina.

"My sense is that unregulated assisted colonization efforts have been relatively benign, so far," said Brodie. "But humans have been moving species to new areas for other reasons for a long time, and sometimes with disastrous consequences."

Risk v. Reward

While assisted colonization carries risks, so does neglecting its use.

According to Brodie, this contention illustrates a need for coherent international policy to help assist in decision-making about where and when the benefits of assisted colonization outweigh the risks.

As it currently stands, the Convention on Biological Diversity (CBD) — the foundational international agreement concerning the conservation of Earth's biodiversity — does not recognize assisted colonization. What's more, the Convention's existing biodiversity goals, last negotiated in 2010, are contradictory regarding the issue.

The CBD mandates maintaining viable natural populations, safeguarding ecosystems and species, and preventing the further decline or extinction of known threatened species — all of which could be enhanced by assisted colonization. The CBD also mandates signatories to prevent the introduction of and to control or eradicate "alien" species that have the potential to threaten biodiversity, goals that could be seen as opposing assisted colonization, said Brodie.

"The strategy is controversial because of concern about introducing new invasive species or just altering natural communities, concerns that may have slowed or stymied policy development and project implementation," said Brodie.

"But if done right, with careful vetting and multi-stakeholder engagement, assisted colonization could be a very important way of preventing extinctions in the coming decades."

Brodie suggested that the ongoing process of negotiating the new, post-2020 CBD goals and targets provides an opportunity to harmonize policy with assisted colonization as a conservation strategy.

"Development of clear policy guidance by a CBD-commissioned technical committee would provide not just governments but also scientists and conservationists with the tools necessary to make informed decisions about when to implement assisted colonization," said Brodie.