Assisted colonization

Assisted colonization (sometimes referred to as assisted migration or managed relocation) is the act of moving plants or animals to a different habitat. The destination habitat may or may not have once previously held the species; the only requirement is the destination habitat must provide the bioclimatic requirements to support the species. The goal of assisted colonization is to remove the species from a threatening environment and give them a chance to survive and reproduce in an environment that does not pose an existential threat to the species. In recent years, assisted colonization has been presented as a potential solution to the climate change epidemic that has changed environments faster than natural selection can adapt to. While assisted colonization has the potential to allow species that have poor natural dispersal abilities to avoid extinction, it has also sparked intense debate over the possibility of the introduction of invasive species and diseases into previously healthy ecosystems. Despite these debates, scientists and land managers have already begun the process of assisted colonization for certain species. Approximately 300 million tree seedlings are planted in the western US, British Columbia (BC) and the Yukon each year. Many climatologists are predicting that the climate could be 3–4°C warmer when those trees are harvested 60-80 years after planting. These changes to climate will expose trees to increased stress and health risks, compromising the many goods and services from the forests. Assisted colonization (sometimes referred to as assisted migration or managed relocation) is the act of moving plants or animals to a different habitat. The destination habitat may or may not have once previously held the species; the only requirement is the destination habitat must provide the bioclimatic requirements to support the species. The goal of assisted colonization is to remove the species from a threatening environment and give them a chance to survive and reproduce in an environment that does not pose an existential threat to the species. In recent years, assisted colonization has been presented as a potential solution to the climate change epidemic that has changed environments faster than natural selection can adapt to. While assisted colonization has the potential to allow species that have poor natural dispersal abilities to avoid extinction, it has also sparked intense debate over the possibility of the introduction of invasive species and diseases into previously healthy ecosystems. Despite these debates, scientists and land managers have already begun the process of assisted colonization for certain species. Climate change is expected to drive many species out of parts of their current ranges while creating new suitable habitats elsewhere. In order to avoid climate change-caused population declines and extinction, many species will need to either adapt or colonize newly suitable areas. Using a niche modeling approach, scientists have predicted that a failure to migrate or adapt will result in about a quarter of the world's species dying out this century under moderate climate change. The natural dispersal rates for many species are far slower than those needed to keep pace with projected habitat shifts in many regions of the world. Prehistoric climatic changes have resulted in massive global extinctions, and the rate of warming projected for the near future is many times faster than changes in the past 10,000 years, Prehistoric climate change events resulted in massive global extinctions, and the rate of global warming that is projected for the near future is significantly higher than the rate of global warming that occurred in the past 10,000 years. The inability of species to migrate in response to human-caused climate change has led to some scientists and land managers to consider exploring assisted colonization as a means for preventing extinction of species. Assisted colonization is a specific type of species introduction. Species introduction is any act of establishing a species in a habitat it does not currently occupy. It often refers to a long-distance relocation, such as the accidental introduction of an invasive species from one continent to another, or the intentional relocation of a species in decline to a habitat where it can persist. By contrast, assisted colonization acknowledges that the natural dispersal rate of many species may be too low to naturally respond to rapid human-caused climate change and instead focuses on where the species would be able to disperse fast enough via natural selection to keep pace with the changing environment. Assisted colonization practitioners consider helping the species disperse into such sites, which are often immediately adjacent to the species’ historical range. In their eyes, assisted colonization represents a small artificial boost to an otherwise natural process. Assisted colonization was initially referred to as 'assisted migration' when it was first proposed. The terminology was later criticized for being reminiscent of natural, cyclic animal migrations in response to changing seasons. The term 'assisted migration' was met with criticism, as it incorrectly inferred human assistance with natural cyclic animal migrations in response to changing seasons. It was renamed 'assisted colonization', as colonization more accurately describes the natural phenomenon humans were seeking. Others have sought to further distinguish assisted colonization from any natural connotation by referring to it as 'managed relocation'. No specific name has been unanimously adopted. Within the scientific and conservation communities the terms 'assisted migration', 'managed relocation', and 'assisted colonization' are often used interchangeably and are understood to refer to the same idea. Even under rapid climate change, dispersal into new areas may not be necessary for some species to persist. Instead of tracking climate shifts through space, some species may be able to survive in their present locations by developing tolerance to new conditions through acclimatization and adaptation. The potential for acclimatization or adaptation to allow persistence in the face of climate change varies by species and is generally poorly understood. One study determined that evolution of higher temperature tolerances in some species of amphibians and reptiles will likely occur fast enough to allow these species to survive a 3 °C temperature increase over 100 years, consistent with low- to mid-range projections of global warming. By contrast, many species, such as most temperate trees, have longer generation times and therefore may adapt more slowly; they may take thousands of years to evolve a similar increase in temperature tolerance. Adaptation this slow would be insufficient for keeping up with expected future global warming if colonization of new habitats is not an option. In addition to acclimatization and adaption, assisted evolution is an alternative to assisted colonization that has been growing in popularity recently due to the worldwide coral reef crisis. Assisted evolution is the practice of using human intervention to accelerate the rate of natural evolutionary processes. There are three main types of assisted evolution. Stress conditioning consists of exposing organisms to sublethal stress, with the goal of inducing physiological changes that increase tolerance to future stress events. There has been documented evidence that some changes can be passed throughout generations in both plants and animals. Stress conditioning can be artificially induced in a laboratory environment to create desired responses based on their environments. Notable examples include a 1989 experiment which used stress conditioning via heat shock on rat kidneys to extend their safe cold storage time to 48 hours. More recently, stress conditioning is being studied as a potential solution for the preservation of coral reefs as they are continually exposed to ocean warming and acidification. Assisted gene flow (AGF) works to increase the presence of desired naturally-occurring genes in offspring. AGF relies on pre-existing genes within the species' genome, rather than the artificial creation and insertion of genetic code within the genome of the species. Assisted gene flow can also introduce related species' genomes into the gene pool to allow for the introduction of previously impossible behaviors into the new species. AGF identifies genes that produce desired behaviors, and works to increase the chance that parental transmission of the gene in question occurs (also known as heritability). Determining which genes within the genome produce desired behaviors consist of experiments which measure the growth, survival, and behavior exhibition of offspring with varying genotypes. AGF is being utilized as a solution to preserve species who are threatened by climate change. Currently, different colonies of the Great Barrier Reef are being interbred to test whether offspring display increased resistance to warmer living conditions. Increased resistance to warmer living conditions allow for the preservation of the Great Barrier Reef even as water temperatures continue to rise. Hybridization refers to the process where an egg and sperm from two different species can fertilize and produce young. Hybridization was studied in the 1800s by Johann Gregor Mendel, who posthumously has been credited with the discovery of genes and alleles and their impact on an offspring's genotype. Benefits of hybridization include the increase in genetic diversity and the potential for genetic combinations which are able to adapt to, and reproduce in, increasingly difficult environments. Hybridization of coral reefs during the annual coral spawning is being experimented with to create hybrid offspring that will hopefully have higher survival and growth rates in a variety of climate change related conditions. Generally speaking, there are three accepted ways that assisted colonization can take place, each one of them with specific benefits and situations in which it applies. They can be defined as reintroduction, introduction and augmentation processes.