Assisted Migration of Trees

There is no shortage of scientific evidence of the current changes in climate that we are observing, and are expected to observe in the near future. With climate change, many organisms are expected to alter their current geographical ranges, in order to combat the effects of climate change and find climatically suitable habitats. Trees and plants are significantly sensitive to climate, and many are already starting to disperse into new ranges in line with the current trends in climate change. But there are many species or populations that will be unable to keep up with the rapid climate change we are seeing, and could be forced out if nothing is done to help them. The assisted migration of species, subspecies or populations is starting to gain more and more interest. Assisted migration can be defined as the human-assisted migration of plants or animals into more climatically suitable habitats or regions. Assisted migration can occur on three different levels,

population level- which is the assisted migration of a population within its current range,

range expansion- which is migration of a species just outside of its current range, mimicking natural range expansion

long-distance- migration of a species far outside its established range, farther than could be achieved through natural dispersal methods

Assisted migration of trees is a somewhat new and emerging concept which has the ability to help stop the loss of biodiversity under new climate conditions. However, there are many unknowns about this concept and many questions being asked. This is why currently most assisted tree migration projects are in the test phase. This past summer, working for a Conservation Authority, I had the chance to help plant one of largest assisted migration test plots in Ontario, into one of our conservation area lands. Most assisted migration test plots involve many different geographic subspecies of tree being planted in blocks surrounded by others, and blocks of local species as well. For example, our test plot involved subspecies of red oak and swamp white oak from Pennsylvania and Tennessee, and these were incorporated with blocks of local red oak and swamp white oaks. The idea behind the test plot is to compare the budding and leafing times of each species, and the overall growth of the trees in comparison to each other and the local species. The Pennsylvania region trees were used because our climate is expected to be similar to Pennsylvania in 50 years, and the same for Tennessee in 100 years. By comparing the growth of the trees in these plots, we can get an idea of the current climate conditions of our region, and which regions’ subspecies of particular trees we should be migrating into our region.

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Assisted Migration test plot, year 3


Pennsylvania Oak planted in an Ontario Assisted Migration Test Plot

Further Reading and References

MNR- Assisted Migration

Assisted Migration and Forestry in Canada

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