World News | How to move without legs or wings: Helping trees migrate to new areas

Quebec, May 7 (talk)

While individual trees are indeed immobile, as a species they can actually move and migrate like birds! However, this happened in a very different time frame.

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That’s what we’ll explore in this article, the first in our new summer series. As researchers in forest ecophysiology, we study fundamental tree physical functions and relate them to wider ecological dynamics. Rapid climate change is challenging the sustainability of forest ecosystems in multiple ways. To tackle new problems related to climate change, we need new tools: “assisted tree migration” is one of them.

To inspire us, an excerpt from a song by Quebec poet Gilles Vigneault:

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Let’s get the definitions out of the way first: Assisted migration refers to “the movement of species assisted by humans in response to climate change.” We usually associate the word “migration” with the movement of people or the seasonal flight of birds.

However, we don’t usually think about forest migration, and it may even seem odd to link the two terms. After all, trees are usually rooted to the ground and don’t move. Or do they?

Tree migration occurs through seed dispersal, germination and establishment of new shoots. After a while, these seedlings will begin to produce new seeds and contribute to this slow geographic expansion.

Migration strategies may vary by tree species. Maple samara, for example, are windborne seeds limited by their weight to travel faster and farther than oak tree acorns. However, it takes years, often decades, for new seedlings to grow and produce seeds that have migrated farther than their parents.

This movement occurs over centuries—often too slowly for our conception of time—and may become limited in the face of rapid human-induced changes in the climate system.

Current climate change is rapidly altering environmental conditions. There has been no natural warming event at a comparable rate in the past. Such rapid change puts enormous pressure on forest ecosystems, not least by altering habitat conditions.

The vast majority of tree species migrate more slowly than their favorable habitats. This means that their migration to new favorable habitats (e.g. colder regions in the north becoming warmer) will not be able to compensate for loss of habitat elsewhere (e.g. warmer regions in the south becoming drier).

This mismatch between changing habitat conditions and natural tree migration has contributed to the loss of forest vitality. Populations of many tree species are expected to decline, which in turn could endanger local forest ecosystems.

We were asked to find strategies to help forests adapt to new climatic conditions. This has prompted researchers and forest managers to consider new approaches to the problem, including assisted migration.

Artificial seed transfer and planting can speed up the natural migration process and help overcome geographical barriers, such as mountains or large bodies of water. As such, assisted migration could be used to help maintain functional forest ecosystems in the future.

This is important not only for species conservation, but also for maintaining all the services forests provide, from wood production to carbon sequestration in the atmosphere.

Generally speaking, relocations over short distances are easier to achieve, while relocations over longer distances require careful planning. Due to the high ecological risk of the latter, it is generally only considered for the protection of endangered species.

But enough theory, let’s move on to concrete examples.

The Sugar Maple (Acer saccharum) is Canada’s iconic tree. As climate change intensifies, sugar maples in the southern part of the region are facing competition from trees like the American beech (Fagus grandifolia) that are more tolerant of warm, dry conditions.

At the same time, the researchers found that areas near the northern boundary of the maple’s range are becoming increasingly hospitable to the species. In this case, assisted migration could help boreal forests adapt more quickly to new conditions and provide valuable services like maple syrup production. So why not keep using this technology?

In 2019, the University of Quebec (UQAC) in Chicoutimi established an experimental sugar maple plantation on the northern edge of Quebec’s Saguenay region. The experiment was carried out in partnership with a local family farm, which has chosen to dedicate part of its land to scientific research and a vision of creating high-yielding sugar trees for future generations.

The plantation, which has 500 young trees from multiple populations in Quebec and the United States, will celebrate its fourth year of life in the spring of 2024. Decades from now, good maple syrup will likely be produced here, along with all the valuable scientific data gathered up to that point.

A similar study was carried out by the DREAM-Québec Research Network, a project of the Quebec government (Ministry of Natural Resources and Forests), the US Forest Service and Université Laval. The experiments included mixed plantations of more than a dozen tree species in the Portneuve region of Quebec and Wisconsin, USA.

Here, the influence of factors such as microclimate, herbivore browsing and plant competition on tree establishment and growth can be tested. In addition, the performance of trees from southern populations—adapted to conditions similar to the predicted future climate—can be compared with that of local populations.

Experimental studies of this type provide invaluable information on characteristics that contribute to or hinder the success of assisted migration projects. For example, we can learn which species or populations are more sensitive to late frost events or browsing by herbivores.

Implementing scientific experiments today can help us fully understand the dynamics and risks of assisted migration so we can make the best forest management choices for future generations.

Climate change is advancing rapidly and forests are not moving at the same rate, so it is important to start planting tomorrow’s forests. (dialogue)

(This is an unedited and auto-generated story from a Syndicated News feed, the content body may not have been modified or edited by LatestLY staff)