Warming caused by climate change is moving the suitable habitat for some plant species farther north in the northern hemisphere. A plant that was once comfortable in one location may be finding it is becoming too warm for it to thrive.
British Columbia, unlike the other Canadian provinces, has changed their rules about replanting forests, hoping to ensure that adapted tree varieties can keep up with the moving habitats. Critics say assisted migration, as it is called, has sometimes produced disastrous results in the past when species were placed in new environments.
Vice’s Motherboard web site has a fascinating article by Stephen Buranyi on the subject. Here is an excerpt:
“The Western Larch can live for hundreds of years and grow to over 200 feet, but the oldest Larch trees in northern British Columbia’s Bulkley Valley are only about four feet tall. In fact, the nearest full grown Western Larch is nearly 900 kilometers south by the US border, which has been the Larch’s natural range for thousands of years. These are the first trees of their kind to be planted so far north.
If the disastrous history of invasive species has taught us anything, it’s that it’s often difficult to predict the consequences of such a change. Ecologists and conservationists generally caution against moving a species outside of the areas they naturally live—a process known as assisted migration—and governments generally agree with this take. Across North America there are strict prohibitions against the large scale movement of living populations.
But for the past seven years the province of BC has allowed millions of trees to be planted toward the northernmost reaches of their natural range and beyond. The government is working with scientists who predict that our climate is changing so quickly that, 50 years from now, when the trees are fully grown, the conditions in the trees’ new homes will actually be more like their old ones.
“It restores the tree to the environment for which they are best suited,” said Greg O’Neill, an adaptation and climate change scientist with the BC government, who helped design and implement the province’s assisted migration program. But while BC scientists think that they’ve acted just in time to prepare their forests for the future, no other province appears ready to adopt assisted migration as a strategy anytime soon.
Many trees are what ecologists call foundational species—organisms whose removal would cause enormous disruption in the ecosystem. Trees are a sort of infrastructure for forests; they bind the soil, retain water, and provide food and shelter. Just like the infrastructure unpinning cities, it takes years to establish a tree population, and they are virtually impossible to move.
And yet, because BC’s northern regions are warming at nearly twice the average rate, much of the province’s 55 million hectares of forest may find that their homes have moved north without them. A 2006 paper from the University of British Columbia applied a climate based model to forest ecosystems and showed that some species ranges could shift by up to 100 kilometers each decade.
Rules in BC require that, as trees are cut down, planters use seeds from the same area to re-plant, preserving the genetic character of the forest. O’Neill and his colleagues produced a forestry report in 2008 that drew on the projected range expansions due to climate change, and their own extensive experiments testing various tree species in different climates. They suggested that the province instead expand the distance seeds could be moved uphill, to track with global warming. Later that year the Chief Forester’s Standards for Seed Use were changed for the majority of BC’s commercial tree species to reflect the suggestions in the report.
According to O’Neill, “these were the first policy changes that addressed climate change in forestry.”
Then, in 2010 the standards were changed again, to allow Western Larch to be planted hundreds of kilometres away from its current range. “That had been a long-standing paradigm that no-one dared transgress,” said O’Neill. One ecologist had even called BC’s migration plans “a little scary.”
It’s difficult to overstate how deeply rooted the aversion to moving nature is for many biologists. In 2009 assisted migration was called “planned invasion” in a report that listed our really awful, truly just stupendously bad track record with species that unexpectedly turn invasive…”