Tuesday, November 27, 2012

Climate Change and Assisted Migration

As gardeners we are, knowingly or not, involved in an act called Assisted Migration. It is definitely a 21st century term and it is defined as,  “Movement of species beyond their historical range either to prevent extinction due to climate change … or facilitate their adaptation to future or projected climate change”, according to Nicole Klenk , a social scientist at the University of Waterloo.  While gardeners of all types from all ages have always coveted what their neighbours had and we did not, we have transported plant and animal species from one country to another, over land and sea, in order to revel in and admire a new discovery, and to own one for ourselves. Today however we are doing this for different reasons, namely the continued survival of plant and animal species, and it is called Assisted Migration. 

Scientists have been studying climate change for a couple of decades and are now seeing ties to the loss of animal and plant habitats. As areas of the earth are warming or cooling we are finding that some species are finding it difficult to adapt to the changes and are therefore at risk. There has been a slow movement by groups and individuals alike to protect the species we love by moving them to locations where they hope they will continue to survive for years to come. 
There are two cases of assisted migration in the news which involve moving a species far from its local habitat. The first is a conifer in Florida, Torreya taxifolia, with a shrinking range in the Florida panhandle. The group Citizens of Torreya Taxifolia Guardians are planting seeds of Torreya taxifolia from private stock or garden centres outside of its northern range in North Carolina. 

Link to Torryea Guardians

A second example headed by Richard Branson of the Virgin Group was to move Madagascar lemurs onto an island that he owns. The plan was to move animals from zoos or private organizations with the intent to protect the species. Conservation scientists criticised him for potentially creating risks to other species on the island. These examples are of citizens making choices on their own (which may be ill informed) and without any government and academic oversight. The concern is that these types of assisted migration may cause more harm by changing native ecosystems. However these actions are also presently perfectly legal.

The philosophy of what we are doing concerns Anthony Ricciardi an Associate professor and invasive species biologist at McGill University. He is not opposed to assisted migration or what he calls assisted range expansion, but the intentional moving of species, such as moving animals to another island. We have a long history of moving plants and animals around the world and have caused some degree of ecological damage by degrading habitat, introducing diseases and pests, and the extinction of native species. Do these long distance introductions such as moving certain plants or animals outweigh the risks of ecological damage? Mr. Ricciardi claims there are no reliable ways to forecast the risks of a species introduction. There are risks with assisted migration such as, creating new invasive species, the effect on the local ecosystem, and the interaction with local species.  He says we need to deal with the root cause rather than moving species around.

The Emerald Ash Borer is quite destructive in parts of Canada and the US. Brought in on packing crates from China.

British Columbia is presently a world leader in a large scale experiment of assisted migration. They are moving 15 tree species (of commercial value) to the northern edge of their range with the intent to study their adaptation to future climate change. They are hoping to develop a seed bank that will be successful in providing trees adapted to a more northern range. To determine success we must wait 15 to 20 years and expect that up to 50% of those seedlings will not survive. 

Professor Sally Aitken in Vancouver, a Forest Geneticist at University of British Columbia, is working on an experiment to save the white bark pine. The white bark pine is listed as threatened in Canada and is in rapid decline in western Canada and USA due to white pine blister rust, the mountain pine beetle, and loss of habitat. This pine has many positive ecological ties to the ecosystem that scientists consider it worth trying to save. As part of a controlled experiment they are moving it by seed within its existing range, to north of its range and in places where it is not expected to survive in BC. The only risk is increased invasion of the white pine, but since it is a slow growing and moving tree the risk is very small, as well, the ecosystem the pines are planted in is already part of its regional flora.
How can we mitigate the impact of carbon emissions on ecosystems? While this is a controversial and difficult problem to solve, we are attempting different ways of dealing with it by assisted migration taken in tiny steps as with the tree studies, and in large steps with the removal of species to areas outside their natural range. Some will argue we need to be working on the root cause. Who is right?

Marc Roberts

(Information taken from the CBC radio program “The Current”)


  1. Ja myślę, że trzeba szukać przyczyn i tu działać. Zmiana środowiska drzew może zaszkodzić roślinności rodzimej. Pozdrawiam.
    I think that you need to look for causes and work here. Changing the environment can harm trees, native vegetation. Yours.

  2. I do believe we interfere too much. We are likely a contributor to the initial problem, but we have a history of making decisions that come back to prove detrimental or ill thought. I agree with Professor Sally Aitken that we have no way to accurately predict the consequence of the action. Great post, Patty.

  3. Thanks for the thought provoking post. I, more and more, like growing plants native to my area, although I also think there may be something to be said for nudging the borders.

    1. Thanks for stopping by Bill. I prefer to plant natives myself, but as I learn more about how plants have and continue to move around the earth it almost seems like a nostalgic endeavor.

    2. I agree that trying to make things 'go back to the way they were' is a nostalgic endeavor and an unrealistic one at that. The world is ever changing and I don't try to stop that. Plus, I continue to plant non natives. I do, though, also try to have a wide variety and sufficient numbers of natives to support a healthy population of beneficial incects and other fauna. And I have to say that a lot of the 'natives' I plant are really only native in nearby states or areas. These are the borders I like to nudge. I'll look forward to your coming posts.