Maple syrup production and climate change: Does the future taste as sweet?

Still seen as a secondary economic sector, maple syrup production is in fact a dynamic industry that imbues new energy into the regions where the next generation is present in numbers. However, climate change is having an impact on sugar maple stands and it is a significant concern to maple syrup producers.

• Canadian maple syrup production is an innovative, growing, and lucrative industry, making Canada the biggest producer of maple syrup in the world.
• Climate change, exotic insects and diseases are becoming more of a threat to maple stands and maple syrup production in North America.
• The maple syrup industry can promote the resilience of current maple stands by using silvicultural practices that increase the vigour of maples and functional diversity of maple stands.
• As climate shifts, it is possible to promote the establishment of maple stands farther north by encouraging the growth of maples where they are already present, and by planting them in a mix with other deciduous species where they are absent.

Maple syrup production, a growing industry in Canada

The use of maple sap, a non-timber forest product, is well-rooted in North American history. European colonists learned from First Nations to use maple sap. Maple sugar then became a key staple for early settlers and was later replaced by maple syrup. For many Canadians, maple syrup production has been a source of income, hobby opportunities and family traditions. But over the last 50 years, Canadian maple syrup production has increased sevenfold, from 11 to 79 million litres (M L). This dramatic increase is the result of technological advancements (e.g., maple tubing systems, reverse osmosis, filter presses, high-performance evaporators), and maple syrup producer groups who had a far-reaching and expansive vision.

Canadian maple syrup production and exports, 2010-2022

What does the future hold for maple trees and maple syrup production in terms of climate change and other biotic threats?

The impact that climate has on maple syrup production in Canada is increasing. Early bud break (bud development) in spring increases leaf exposure to late frost and the risk of damage to new developing tissues. This late-frost damage is possibly more significant than exposure to early frost in the fall. If such events become chronic, frost could reduce annual wood growth and the accumulation of reserves.

The maple sap season is also starting earlier than in the past. By the end of the century, the season is expected to start another two to three weeks earlier because of the earlier spring. Despite this, the effects of climate change on maple syrup yields are less obvious. Some authors predict that maple syrup production in Québec will increase due to higher temperatures, whereas others foresee little change. However, these predictions do not consider upsurges in extreme weather events (e.g., prolonged droughts, false springs and/or late frosts, periods of extreme heat) and epidemics of alien insects that could have a negative impact on the vigour and survival of our maples, and consequently, maple syrup production.

What can we do to help maple stands?

The maple syrup industry is aware of the impact of climate change and other biotic threats on its activities and is committed to both preserving maple stand health and increasing their adaptive capacity. To that end, silvicultural strategies may be implemented to mitigate climate risks and other threats to maple syrup production, such as:

• liming for select trees or stands, which increases the vigour of maples, enabling them to recover better in response to climate or biotic stress
• thinning, which aims to reduce the water demand of maples during periods of extreme drought
• diversifying, by maintaining a certain number of companion species with complementary functions (functional diversity) in maple stands to promote stand resistance and resilience

A slow march north for maple stands

Maples will take hundreds of years, if not more, to migrate north naturally and follow their climate niche. In fact, the strong presence of conifers affects the germination capacity and growth of maples, slowing down their migration. However, there are forest management tools that can help to counter these limiting factors and facilitate their progression to new territories.

When maples start naturally colonizing more northern forests, it may be possible to increase the growth of young maples through thinning. The purpose of thinning is to reduce the number of conifers that slow down the establishment and growth of maples, while increasing the amount of available light. This type of management could facilitate the transition of mixed forests to maple stands. Where maples are absent but weather conditions permit, it may be possible to plant them with other deciduous species that improve the soil to facilitate their establishment and sustain their growth. Such movements, which constitute a form of assisted migration, are best limited to modest northward distances (e.g.
< 200 km) to reduce survival risks of the migrated planting stock and to the recipient ecosystem.