Earth Day 2017: Blogs from the Wildlife Conservation Society
By Donald Reid
April 20, 2017
[Note: this piece was adapted from a longer article that appeared originally at the WCS Canada Muddy Boots blog.]
Viewed from afar everything appeared dull and dead. Black and grey skeletons of trees stood above the browns of exposed soil. The vibrant pines and willows I’d seen here before had been scorched away by fire. I knew to expect it but was astonished by the sight. Yet walking through the burn, I was struck by a different sign of change. Brilliant dabs of green poked out of the ground everywhere. Young pines were growing from seeds in cones burst open by the fire’s heat.
Human beings often have a conflicted view of change. We like certainty and stability. In conservation, however, we have learned that living with certain changes is essential because they create the conditions for many species to thrive. Lately, however, climate warming is creating new and different kinds of changes, often taking place more rapidly than we are accustomed to.
Conservationists tend to separate ecological change driven by “natural” events from change driven by human activities. Researchers hope to understand how natural disturbances such as wild fires occur in space and time, and how various species respond in stages after such disturbances. Although disturbance brings instability, the whole ecosystem passes through predictable changes before another disturbance hits. In other words it’s “resilient.”
Take the boreal forest. Certain beetles, and the woodpeckers that thrive on them colonize recent burns because the beetle larvae eat the cambium of recently killed trees.
Within a few decades of the fire, shrub-rich growth dotted with small conifers provides a wonderful mix of food and shelter for moose and snowshoe hares that don’t like the open spaces of a recent burn or mature forest. Where the hares proliferate, lynx follow because they rely on abundant hares to be able to get enough energy to raise kittens.
After many decades the growing trees shade out the shrubs. If this maturing forest escapes fire long enough to thin itself out, ground lichens can colonize and support a caribou herd.
So, in boreal forest management, we need to “emulate” such natural disturbances in the way we log. This includes creating large cut blocks with representative unharvested patches to support healthy populations of species that rely on young forests.
Lately climate change has put a major wrinkle in this cycle by triggering new trends in temperature and evaporation that determine how often fires occur and how well plants grow. Despite being adapted to disturbance, boreal species may now be forced to contend with more rapid, frequent, and intense changes. As the range of tolerable growing conditions for species moves north or to higher elevations, we’re left wondering how many boreal plants will respond.
Major thaws followed by re-freezing are now much more common in many boreal and arctic regions. The snow gets an ice crust, or melts completely away from some areas. Without a fluffy insulation of snow, many plants, insects and small mammals die back or lose their local habitat, and larger animals such as caribou find it a lot harder to get through the snow to their food.
So while boreal species may be well adapted to shifting conditions following fire, the novel effects of climate change are a different beast.
In Yukon we are trying to understand how these changes in climate may drive changes in our ecosystems. Working with researchers at the University of Alaska, we have projected that by the end of the century: southern Yukon’s forests may have displaced arctic tundras; forests could also move upslope, at the expense of alpine tundras; and prairie grasslands may dominate southern Yukon valley floors.
These are startling changes. Plants that can thrive in their new circumstances will do well. We are already seeing that in tundra habitats where woody shrubs are growing bigger and expanding their local distributions.
Whether or not the plant types will move as projected is rather uncertain. Few plants can suddenly pick up and move to follow the shift in the growing conditions to which they are adapted. In mountainous regions, wide valleys and the ranges themselves block many species from shifting their distributions in response to growing changes.
These species are essentially trapped unless they receive assistance to “escape” to new locations with suitable habitat. It seems certain that they’ll need our help, but that’s only fair. It is humans who are forcing the climate changes, and we must work to slow them down and help the organisms adapt. How to do this is one of the conundrums we face.
Given the uncertainty around climate change impacts, scientists agree that monitoring changes in in weather conditions, snow conditions, vegetation composition, wildlife abundance and their inter-relationships is a high priority. Although we cannot anticipate all changes, tracking them in as close to real time as possible is the next best thing.
We face another conundrum though. The changing climate will not be responsible for all the changes we observe in our monitoring. More likely we are seeing complex interactions of different factors. We face a big challenge in teasing out which changes would have happened in any case, which result from a warming world, and which result from our other diverse activities. Interpreting the evidence has become more challenging.
— — — — — — — — — — — — — —
Dr. Donald Reid is Northern Boreal Mountains Landscape Leader for WCS Canada.