Assisted migration

• 1. Defining The Movement

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  The phrase assisted migration describes the intentional establishment of populations or meta-populations beyond a species' historic range. This tactic moves plants or animals to geographic locations better suited for their present or future habitat needs. Species unable to migrate or disperse on their own receive this human intervention. Conservation biologists first used the term in publications during 2004. They intended it as a method to reduce biodiversity losses caused by climate change. By 2007, researchers offered synonyms like assisted colonization and managed relocation. A paper with 22 coauthors later popularized the latter term. Forestry science discusses the concept differently than conservation biology does. Paleoecologists had already noted significant lags in northward movement of dominant canopy trees since the final glacial retreat. Researchers began applying climate change projections to tree distribution modeling efforts in the 1990s. British Columbia became the first provincial government to update seed transfer guidelines with what they call climate-based seed transfer.

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• 2. Forestry Versus Biology

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  Debate concerning the ethics of assisted migration in forestry practice was both short-term and muted compared to that which prevails in conservation biology. Migration remained the standard term used in paleoecology for natural movements of tree species recorded in the geological record. Translocation terminology was not controversial among forestry researchers because of this historical context. The former field is necessarily guided by seed transfer guidelines whenever timber or pulp harvest follows reforestation plantings. A separate Wikipedia page titled Assisted migration of forests in North America launched in 2021. It serves as a teaching tool for climate adaptation education within the forestry profession. Conservation biologists focus on endangered species management where risks feel higher. They worry about invasive species potential when moving organisms into new ecosystems. Forestry scientists prioritize timber production and forest health over these specific ecological fears. This divergence created two distinct communities discussing similar actions under different ethical frameworks.

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• 3. Invasive Species Risks

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  Scientists fear relocated species might spread diseases or become too successful in recipient ecosystems. The principal concern involves the potential for introduced species to drive out native flora and fauna. Most agree that assisted migration efforts should involve detailed planning and risk assessment unlike accidental introductions. Mueller and Hellman reviewed 468 documented species invasions and found only 14.7% occurred on the same continent where the species originated. The vast majority of those were fish and crustaceans. Terrestrial species that became invasive on the same continent often crossed large biogeographic barriers like mountain ranges. Expected uses of assisted migration generally involve helping species colonize habitats immediately adjacent to their current ranges. Those who wish to keep the practice on the table note very few invasions resulted from short-distance movement. Yet some argue any threat of introducing invasive species disqualifies assisted migration as a viable response. Uncertainty in predictive niche models limits confidence in decisions regarding future suitable habitat.

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• 4. Evolutionary Alternatives

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  Stress conditioning consists of exposing organisms to sublethal stress to induce physiological changes increasing tolerance. A 1989 experiment used heat shock on rat kidneys to extend safe cold storage time to 48 hours. Researchers study this method as a solution for preserving coral reefs exposed to ocean warming. Assisted gene flow works to increase presence of desired naturally occurring genes in offspring without artificial code insertion. Different coral colonies of the Great Barrier Reef are interbred to test whether offspring display increased resistance to warmer living conditions. Hybridization refers to the process where an egg and sperm from two different species fertilize and produce young. Cupressus abramsiana serves as an example where hybridization could result in loss of biodiversity. The 2016 federal update warned of dangers of genetic introgression threatening the integrity of this cypress tree. Outbreeding depression reduces fitness when population growth rate falls below replacement rates wasting reproductive potential.

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• 5. Global Policy And Law

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  A review paper published in Science in 1989 compiled translocation use for rare species from 1973 to 1989 across multiple nations. Climate change was not mentioned as a cause for concern in that document. Three decades later, the International Union for Conservation of Nature reported climate change affects at least 10,967 species on their Red List. In another publication in 2021, climate change appeared 20 times but assisted colonization was mentioned just once. The United Nations Convention on Biological Diversity recognized climate change as the third most significant threat to global biodiversity in 2022. No mention was made of conservation tools like translocation within the agreement's goals. Although the Endangered Species Act of 1973 did not restrict assisted migration initially, regulatory changes in 1984 made prospective translocations more difficult. June 2022 saw the U.S. Fish and Wildlife Service publish a proposed rule to revise section 10(j) regulations. The final decision scheduled for June 2023 aimed to delete reference to historical range parameters for experimental populations.

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• 6. Case Studies Of Action

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  The Florida torreya is a critically endangered tree found at the state border region of northern Florida and southwestern Georgia. A self-organized group called the Torreya Guardians formed in 2004 to undertake its assisted migration. By 2018 citizens documented species thrival in dozen legacy horticultural plantings including seed production. Their own plantings in Cleveland Ohio began producing seeds that same year. The western swamp tortoise represents the first example of an endangered vertebrate experimentally translocated due to climate change. First trial began in 2016 with release of 24 captive-raised juveniles into distant locations. Lead scientist Nicola Mitchell spoke about ethical imperatives regarding human responsibility toward this reptile. Second trial started in 2022 within Scott National Park continuing into 2023. In Mexico City volcanic regions scientists reported positive results from combined projects involving Abies religiosa trees. Thirteen researchers coauthored a paper concluding establishment of these trees at 3,600 and 3,800 meters is feasible.

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