Photo: An example of a forest. Hawk Mountain Sanctuary, PA, USA.

This past summer and autumn were the worst forest fire seasons up and down the west coast of North America in a long time. In British Columbia it was the worst season ever flat-out. California and Oregon were suffering wild-fires right through into autumn. Forest fires happen. They are a natural process of rejuvenation for forests, for sure, but this natural process is having a brutally harsh impact on us. This past season has displaced tens of thousands of people, disrupted communities, and destroyed homes and businesses. This year forest fires have cost the American people over $2 billion battling them and the people of BC over $300 million. In total over 8.5 million acres of the west has burned this year.

Those figures at least gives us some quantity, some size of something to grasp to. Though, those are still really staggering numbers I find difficult to get a sense of scale over. The destruction is so much more than just the monetary and geographical impact, though. Thinking of people’s lives that have been wrecked because of this, the business lost, the ecological disruption is such a greater cost that can’t really be quantified appropriately but is by far the most significant aspect when addressing the destruction of forest fires. But among all of this there’s another worrying undertone – fire seasons are becoming longer and forest fires/wild fires becoming more prevalent.

I mean, this isn’t too surprising when we think about it. Climate change is happening and the associated trend of changing weather patterns with the seasons with drier summers has been observed. But here lies the really worrisome thing about the effects of climate change, there’s going to be downstream effects. Climate change causing one event resulting in another and another rippling out affecting more and more aspects of our environment. And there’s so much potential that these changes will be completely unforeseen or predictable by us then catching us very off-guard.

Coming from the perspective of a microbiologist, one thing I see being particularly troublesome is that forest fires and their increasing frequency and greater spread could potentially eradicate biodiversity and irreparably damage whole ecosystems. Forest fires are a mechanism of recycling in ecosystems. Nutrients and minerals and basic compounds are reduced and reused. Carbon and nitrogen in particular are actively cycled in ecosystems. And microbes are the foundation of this cycling.

Bacteria, fungi, archaeans, and protists have close interactions with each other but also with their macroscopic cohabitants, plants and animals. Most importantly here are the interactions with what really makes the forest, well, a forest – the plants.

Fungi and bacteria in particular have been well studied and have very close relationships and symbiosis with plants either through breaking down dead plant matter or symbiotically living on plant roots. Microbes living in forest soils are absolutely essential for taking plain carbon and nitrogen, or inorganic forms of molecules and minerals and producing more complex, more energy rich organic molecules that plants as well as others use. Not all microbes do this but the ones that do are simply but very appropriately called primary producers.

There’s complex interactions between the primary producers and all of us that benefit and rely on them that really aren’t fully understood. We just don’t entirely know how deep our relationships go but it is certainly appreciated that there is a necessity to have diversity of microbial primary producers and microbes in general to have a healthy ecosystem. The main problem that seems to be emerging is that fires ablate the biodiversity of a forest, trees and microbes alike are burned. Of course, the forest regrows. Every variety of life re-establishes itself, nature abhors a vacuum. However, not everything comes back at the same rate.

This is where climate change causing longer and more severe forest fire seasons may be destroying the long-term health of our forests and biodiversity in them. After a fire, plants (trees, ferns, grasses, mosses, etc) are the first to rebound and regrow. Microbes are slower to reach the levels of diversity that they were pre-fire. Certain species will re-establish themselves almost immediately after a fire but overall the diversity of species and primary producers will remain limited and take as much as 15 years to get back to pre-fire levels of biodiversity. Forest fires in general are widely dispersed and isolated across the vast forests of the west. It’s not the same spots that burn every year but fires occur sporadically in different spots year to year. It’s typically decades between one particular area experiencing a significant fire. So, not too bad then if it only takes 15 years to get back to pre-fire biodiversity and productivity in an ecosystem. The problem is that if rates of forest fires keep increasing there may be a tipping point where forests as we know them may never be able to re-establish a healthy ecosystem.

Changes to forest dynamics and composition is actively being studied in Alaska where the greatest changes due to warming trends have been seen in the Arctic (here’s just a few research papers to get an idea: 1, 2, 3). This could create a scenario where the plants that re-establish ahead of primary producer microbes are taking more from the environment than is being cycled back in. Plants (and animals, and well, everything not a primary producer) will literally be eating up energy rich sources of nutrients and producing waste while there won’t be any significant populations of primary producers to cycle nutrients and maintain a healthy balance. The long-term effect could see forest soils become nutrient poor fundamentally changing forests and potentially causing ecosystems to start circling the drain rather than cycling nutrients.

This would affect us completely in every aspect of life from the most important of living sustainably with our natural world to whole economies. Fortunately, there are a lot of scientists aware of this possible outcome and are working their asses off studying the effects of fire on forest ecosystems. Parks Canada very recently started a study on Tumbo Island in the Gulf Islands Reserve in southwestern BC to investigate controlled burns as well as resulting effects on the ecosystem.

Climate change is a very real threat to all of us and everyone coming after us. This is a relatively rapid change and we’re only just now starting to see how it’s gaining momentum to affect even the most minute parts of our environment and in ways we can’t predict. Things are going to change, and already are, that’s a certainty. But with some science and stewardship we can all (macro- and microscopic) be adaptable to this. There’s that tried and true wisdom of some old bear reminding us something along the lines that only we can prevent damaging our environment.

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