Can tree genomics help us plan for the future?

British Columbia’s forests are changing. Climate change is altering the habitable zones for plants, and in a province where exports to the United States alone were worth $2.5 billion last year, a tree falling in the forest here will be heard across the province.

AdapTree is a UBC project led by Dr. Sally Aitken, UBC Forestry Professor and Peter Wall Institute Scholar. The project aims to understand how forests are reacting to climate change, and what actions the province’s forestry sector can take to help forests adapt effectively. Simply put, the project aims to understand where trees have historically been in order to better understand where they should be in the future.

“We know that those climatic niches are moving way faster than these tree species have historically been able to move,” says Dr. Aitken. This “colonization lag” or “migration lag” presents a challenge to the forestry sector, but that same sector is in the best position to mitigate the problem.

Forestry companies in the province plant 250 million trees each year, meaning that humans are influencing, and to some extent even controlling, the spread of genes. That is good news: it means that with the right information in hand, there is an opportunity to assist the adaptation of forests by relocating the right genomes to the right places in the course of normal business operations.

“We can at least increase diversity,” says Dr. Aitken. More diversity in the genomes of a population makes it more resilient, and with unpredictable and complex changes taking place, resilience is key to the health of the forest. At best, trees with the right genes can be selected for the right habitats, increasing the rate of gene flow to the areas that best fit those genes.

The former “local is best” strategy for replanting trees no longer applies, according to Dr. Aitken. “All of a sudden, local doesn’t work as well anymore.” The AdapTree program will be making policy recommendations to the province to help modernize the thinking using data from across the province.

Dr. Aitken (right) and former PhD student Sierra Mclane show off seeds while planting an experiment with the endangered species whitebark pine near Whistler. In addition to projects focused on how forest management can help trees adapt to climate change, Dr. Aitken is investigating the ability of native tree species to tolerate climate change.

To understand what’s happening in BC’s forests, Dr. Aitken’s team has assembled an impressive amount of genetic data. She spouts numbers with the seasoned manner of someone used to explaining a complex project. If printed out on normal sheets of paper, the amount of data collected so far – 8 to 10 million genetic markers on two species of trees are being examined – would make a stack of paper 150 kilometres high.

Some ranges are predicted to expand as the northern parts of Canada grow warmer and invite southern species in. However, Dr. Aitken’s lab is focused on the shift of genes within the existing ranges, and the effects of those shifts on existing populations, rather than the expansion of their limits. Even the movement of genes within species ranges is complex enough, as populations of a species can be specifically adapted to their preferred habitat. Diluting those genes with outside individuals is known as outbreeding depression. And the different genomes of one population as compared to another can be so different – even within a species – that they develop genetic incompatibilities.

“You run the risk of disrupting [local adaptations] when you move things around,” explains Dr. Aitken. “So we really need to understand that on a species-by-species basis.”

Her work is also focused on solely abiotic factors: things like climate and water availability, rather than biotic factors like pests and disease. But, she acknowledges, as the climate warms, “insects and diseases are going to play a big role.” However, trees growing in their optimal environments are naturally healthier, making them more resistant to pests like the mountain pine beetle.

Research like AdapTree is crucial for the future of BC’s forests and forestry industry. Foresters have been enthusiastic about the project, voluntarily sending in seed and seeking advice.

“They see that things are changing,” she says. “But… when you’re planting a tree that needs to live at least 70 years, how do you know what to plant?”