The impacts of climate change on wildlife range
According to Canada’s Changing Climate Report, the global climate is currently warming at an alarming rate, largely as a result of human activity. Warming in Canada is occurring at twice the magnitude of the global average, with even higher rates in northern regions. The Earth’s global average temperature is projected to increase between 2-5 degrees Celsius by the end of the century.
These rapid changes in our climate are causing changes in both biotic and abiotic factors that are pushing many plants and animals to higher elevations and latitudes in search of better living conditions, effectively altering their geographic ranges. In addition to range, animals are also changing their behaviour and lifecycles. For example, changes in in the onset and length of seasons can influence the timing of migrations and certain life-cycle events such as mating.
Today, approximately half of all species are on the move, with terrestrial species shifting on average 17 km towards the poles and 11 m in elevation per decade. The rate is four times as fast for marine species.
Let’s explore a few of the consequences of these changes in range.
MIGRATION
First, let’s look at the impacts on migratory species, for whom these changes will be largely negative. Animals use predictable cues in their environment to time and navigate their migrations, so understandably, abrupt changes in these cues will changes things like their departure dates, arrival times, mating, and birth of young. Given that migration is often timed around food availability, if this window does not align with the timing of birth or hatching, it can lead to population declines in animals like birds. Changes in water temperatures can also impact the metabolism and physiology of migratory water species (such as salmon), threatening their health.
In addition to this, some species (ex: Canada geese) have reduced their migrations altogether, forming sedentary populations. This can be a problem because large groups of animals that would normally separate from one another now aren’t doing so, which can increase the spread of infectious diseases.
For example, monarch butterflies in the US that have recently formed nonmigratory populations are being infected with a protozoan that is significantly shortening their lifespan. Because migratory species influence biodiversity and ecosystems on large scales, changes in their behaviour and distribution have the potential to countless other species that interact with them.
PREDATOR/PREY DYNAMICS
Changes in range can also impact important predator-prey relationships because a change in vegetation pattern as a result of increased temperature or precipitation can lead to a change in the distribution or abundance of prey species, such as grazing ungulates. This can then alter the abundance of predators.
In regions with multiple predators, one predator species might respond more favourably to climate change, altering competitive relationships too. For example, a changing climate in Newfoundland has resulted in an increased risk of predation on caribou from coyotes while reducing the risk from black bears. The long term effects of this could have significant impacts on future caribou numbers. These population dynamics can shift key relationships that are then felt throughout the food web.
LOSS OF SUITABLE HABITAT
Climate change won’t impact all species the same way. Many won’t be able to shift to an alternative habitat due to their specialized diets or need for specific habitat features, such as alpine species. Others may already be at the limit – for example, as Canada’s boreal forests shifts northwards into the tundra, Arctic species such as arctic fox and snowy owls may lose the only habitat they are adapted for.
One study based out of Alberta looked at 12 key boreal species and modelled how projected changes in the climate will affect these species over the next 60 years. The results suggest most species will see a reduction in range and/or a shift toward the north. For example, boreal chickadees are estimated to lose over 30 percent of their habitat by 2080, and caribou will lose more than half.
As for the few species that succeed and find a new place to call home, they face interactions with species they have never seen before. For example, grizzly bears are generalists that may actually be benefitting from warmer weather in Western Canada, due to the fact that it increases their foraging season and opens up new habitats up north. Recently, they have been reported as far north as Inuvik, Northwest Territories. However, a move into the north will inevitably expose them to increased competition with polar bears, a species they don’t naturally encounter. The long-term impacts of this are unknown, with possibilities including predation of one bear on an another, one bear outcompeting the other, or even hybridization… which has complex conservation implications. While some relationships between species that have coevolved over millions of years will be broken, other animals that were never meant to encounter one another will collide.
It’s incredibly difficult to predict the cascades that will ensue from the displacement of even one species, let alone many. The effects of climate change have the potential to cascade in multiple different directions and across various domains, making it difficult to manage the consequences.
CLIMATE FEEDBACKS
Lastly, the movement of some animals may actually shift ecosystem processes in such a way that these movements amplify future climate change. One article in the Smithsonian Magazine found that with warmer temperatures increasing vegetation at northern latitudes, beavers have been moving up into Alaska, creating over 12000 ponds in regions where there were none just 50 years ago. The issue is that the pools beavers make when they build their dams are increasing the amount of surface water in the area, causing surrounding ice to warm and permafrost to thaw. Because thawing permafrost will result in the release of greenhouse gases that have been stored for thousands of years into the atmosphere, a process that drives climate change, we end up with a feedback loop, where the beavers whose change in behaviour is the result of climate change are now unknowingly causing more of it.
All this information prompts us to consider the broad implications of so many animals changing their geographical ranges. It is undeniable that these shifts will cause changes in both the distribution and abundance of biodiversity, both locally and on a global scale.
Species redistributions will also have impacts on public health, as some species such as disease-carrying insects, parasites, and bacteria expand their ranges into new areas, due to the fact that warmer temperatures will enable them to survive winters and accelerate their reproduction. For example, the deer tick has expanded its range across North America, which increases the risk for Lyme disease in regions that previously didn’t need to worry about it. The Government of Canada reported only 143 cases of Lyme disease in 2010, and as many as 987 just 6 years later, indicating a growing risk. Additionally, the mosquitos that carry malaria, dengue, and Zika are also expanding their ranges.
While it’s tempting to call all migrants “invasive species”, some ecologists are raising the point that we will have to be cautious with our use of that word going forward. While the term carries a negative connotation, it’s important to note that many of the shifts in ranges that we will see over the coming decades are essential to the survival of species that are simply trying to survive extreme climactic changes. Rather than jumping to judge these movements as something negative, we’ll need to consider the ethical complexity here, with the reality being that many of these “invasive species” are actually refugees of a climate emergency that humans have created.
This information begs the question, what is our moral responsibility in helping these migrants, and what can be done to responsibly assist them as they move to find refuge in a changing world?
Well for starters, we need more research. While range changes have been reported, the implications that they will have for biodiversity, ecosystem services, public health, and climate feedbacks are not yet well understood.
Secondly, we need to continue to address the other threats that we pose to wildlife, including pollution and habitat degradation, to boost the adaptive capacity and resilience of wild species so that they can better adapt to climate change.
We need to support climate programs that promote climate literacy, the reduction of carbon emissions, and adaptation plans that protect ecosystems, including reducing or banning development in environmentally sensitive areas.
We also need to find ways to enable wildlife to shift their ranges as needed by expanding protected areas and increasing connectivity between them. Although this is difficult because we don’t know where threatened species are going to be in 10 or 100 years, one such effort is the Yellowstone-to Yukon project, which is a joint effort between Canada and the US to preserve a strip of land from one region to the other, to allow a north-south corridor for wildlife to safely move through.
Assisted colonization may also become a conservation tool that we can use to move populations to areas where they have a higher probability of survival, although the challenge would be identifying when and with whom this is appropriate, to avoid unwanted consequences and cascades.
Lastly, given that the risk of cascades in this situation is high, there will be a need for systems thinking that teaches policymakers how to identify cascades and predict the long term consequences of their actions, by recognizing the many interdependencies at play here. Rather than focusing on one aspect of climate change, we ultimately must learn to view the system as whole, to enable comprehensive mitigation and adaptation strategies to climate change that allow us to protect the wild species with whom we share this one planet.
REFERENCES
Allen, K. (2017). The great global species shakeup. Toronto Star. https://projects.thestar.com/climate-change-global-species-shakeup/
Aridi, R. (2022). Beavers are reshaping the Arctic tundra. Here’s why scientists are concerned. Smithsonian Magazine. https://www.smithsonianmag.com/smart-news/beavers-are-reshaping-the-arctic-tundra-heres-why-scientists-are-concerned-180979325/
Bastille-Rousseau, G., Schaefer, J. A., Peers, M. J. L., Ellington, E. H., Mumma, M. A., Rayl, N. D., Mahoney, S. P., & Murray, D. L. (2018). Climate change can alter predator-prey dynamics and population viability of prey. Oecologia, 186(1), 141–150. https://doi.org/10.1007/s00442-017-4017-y
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