Gene editing and the war against the Pine beetle

Anais Gill in Year 11 shares with us her Unconquered Peaks article about how gene editing can prevent outbreak of harmful pests on our environment due to human activity 

Driving up Highway 40 in Alberta, Canada, a couple summers ago, my eyes were glued to the expanse of harsh, red dead-standing forest climbing the mountains. This would turn out to be one of the most significant forest disturbance episodes recorded in North America. 

These dying red pine trees were due to the ongoing outbreak of the Mountain Pine Beetle (dendroctonus ponderosae, referred to as MPB). The size of a mouse dropping, it has now devastated 20 million hectares of pine forest in North America since the outbreak began in the early 1990s, approximately the size of England and Scotland combined. This outbreak, with its severity caused by climate change, has had many impacts on the environment, the economy, and public safety given increased forest fire risk. However, new and controversial research into tree gene editing may be a solution to this problem by providing a defence against the MPB. 

The MPB historically is native to western North America. It invades the tree trunk and overwhelms the tree’s ability to produce resin to defend itself. The vast numbers of attackers feed on phloem in charge of the distribution of nutrients, which cuts off the transport of nutrients in the tree. Tree foliage dries up as conduction of water up the tree is interrupted by the infestation. There is a gradual change of colour of the foliage, from green to red (this takes around a year). The needles then fall off and the tree appears grey. 

Normally, the beetle population is so low that they can barely kill one tree, and those they do kill are already weak or diseased. Outbreaks are natural disturbances and happen every few decades or centuries. These outbreaks have a trigger, which is a change in climate to warmer and drier conditions. It elevates MPB populations, which allows greater productivity and greater survival rates for their young. These warmer and drier conditions also lead to drought, posing stress on pine trees and lowering their defences. Once beetle numbers have risen, there are so many beetles that pine tree defences are overwhelmed. This leads to beetles attacking healthy pines, as it provides better food for their young. Once this cycle begins, it is difficult to stop; the outbreak is now self-perpetuating.  

This current outbreak is far outside the historic norm: it is said to be ten times bigger than usual. The beetles have killed millions and infected billions of trees. They have moved several hundred kilometres north to reach the Yukon, spread east across the Rocky Mountains to Alberta and Saskatchewan, as well as higher in altitude. The MPB has been meeting new species of pine in the Yukon, making the beetle an exotic insect, therefore harmful to native ecosystems.  

What makes it more concerning is the fact that the only natural way for the outbreak to end is for it to reach completion, for most of the pine trees in the landscape to be dead, leading to a drop in beetle population due to lack of food. The only other way for it to naturally end would be for the climate to become colder and wetter. In the past, outbreaks would be caused by abnormal warmer and drier periods, and the beetle population would be controlled as the climate eventually returned to normal. Because of climate change, we cannot depend on this to end the outbreak: winters are gradually warming up and becoming milder, which allows the beetle to survive the coldest months it would normally die in. 

The impacts of this current outbreak are numerous. Not only does it damage forest ecosystems and biodiversity, which reduces habitat for native wildlife, but it has harmed the economy, heightened fire hazards, and created a carbon source. 

As a result of the abnormal outbreak, there has been a decrease in pine supply, which has negative socio-economic consequences for communities reliant on the forestry industry. Over 55,000 jobs have been impacted in Northern Ontario. In the province of British Columbia, the government has spent over $917M fighting the beetle since 2001; the Federal government of Canada has spent $340M since 2002 and has committed an additional $800M towards the cause. 

Another concern is the heightened fire hazard in the affected areas. A forest with dead trees and dense dead foliage is the highest category of fire hazard. This is an issue because Canadian wildfires have intensified during heat waves, and large expanses of dead pine forest only worsen this problem as they are a major source of fuel. This summer, the village Lytton in British Columbia was destroyed by a forest fire, after three consecutive days of record-breaking temperatures far beyond anything recorded in Canada before. Prolonged drought caused by lack of rainfall is also a contributing factor. 

Finally, the expanse of dead forest reduces carbon uptake and increases future emissions from the decay of killed trees. Forests are important carbon sinks, but when vast areas are destroyed, they become sources of carbon. In the worst year of the outbreak, carbon emissions from the MPB-impacted areas in British Columbia alone are estimated to have equalled the carbon releases from fires all across Canada for the preceding 40 years. This is an issue because forests around the world have moderated climate change by absorbing one quarter of carbon emitted by human activities, and they are unable to do this if they become carbon sources themselves. 

An ongoing project and reforestation strategy has been researching the genetics of lodgepole pines, specifically the distinct DNA markers the few surviving pine trees contain. Researchers have been looking at the modification of pine trees that resist the pine beetle. Janice Cooke (University of Alberta) has led this genomic research project, and reports that DNA screening shows the beetle-resistant trees share similar genetic “fingerprints”. 

This project has analysed pinecone seedlings grown from seeds gathered from infected stands in British Columbia. It is conducted in partnership with Genome Alberta and Ontario Genomics and received $6.4M in federal support in July. It aims to reforest impacted areas with beetle-resistant seedlings to “help a new generation of hardier forests take root” and enhance the resiliency of forests replacing these areas. It also plans to prevent the eastward spread of risk potential into Alberta. Researchers are now analysing samples from outbreak zones in Alberta and British Columbia to see if the genetic fingerprint can be found. 

This is a promising project, as if it is successful, it would reduce the likelihood of future MPB outbreaks of this size. However, many environmental activists oppose genetic research and genetic modification. They say that genetically engineered trees that are released commercially risk contaminating native forests, damaging ecosystems, and harming communities, because we do not know the long-term risks they pose. These are risks and issues that will need to be monitored if this research proves to be the solution to this MPB outbreak. 

Pine forests in Western Canada are at extreme risk from both the beetle and climate change-induced forest fires, which also cause significant public safety and economic concerns. But it is important not to class the Mountain Pine Beetle outbreak as a local issue, because its implications are global. Similar dangerous beetle outbreaks are prevalent in other areas, such as the pinyon bark beetle attacking forests in southwestern US. New research into gene editing gives us some hope that the impact of the beetle and prevention of further attacks can be better managed in Canada and around the world. And it provides a promising avenue for future research to help us control other impacts of climate change.