As across the Earth, the impacts of climate change are playing out here in British Columbia. We see this in longer summer droughts, and in more frequent and damaging winter floods. As we attempt to adapt to and mitigate the changing climate we have created, everything about our society from infrastructure to food production systems needs to adapt. However, humans are not the only beings who must adapt to a changing climate.

Range shifts

Climate change is affecting temperature and rainfall patterns around the world, and as a result some plants and animals are leaving the places where they were historically abundant and are moving to new habitats. All living things have criteria that need to be met for survival. These criteria include specific ranges and timing of temperature and rainfall, as well as ecological factors such as predator-prey dynamics and competition for resources. When environmental factors change, the geographic boundaries that a species can survive within change as well. This is known as a range shift, range expansion, or range reduction depending on the circumstances.

To conceptualize a range shift, think of a mountainous region that is getting warmer every year. Plants and animals that were once limited to valleys due to cold temperatures at high altitudes could expand their range up the mountain slopes as the area heats up. While this happens, the species that once lived on the mountain tops might get squeezed out and disappear.

Range shifts have the potential to affect Mayne Island’s varied ecosystems in unexpected ways.

Mobile animals like fish are sometimes better able to shift their ranges than stationary organisms such as trees. However, the complexity of factors affecting the survival of any given species makes it difficult to predict exactly how range shifts will occur over the next decades. The ability to move to new habitats does not guarantee success upon arrival. Most species have evolved to survive in very specific conditions which cannot be found outside of their current range. In addition, a drastic reduction in available natural habitats over past centuries driven by human development makes moving to a new home more difficult or impossible for many species. Commonly, species surviving in remnant patches of habitat in wildlife preserves and parks may have nowhere to go when climate change makes the small amount of habitat remaining to them uninhabitable.

Although the ways in which range shifts will affect Mayne Island and the waters around it are yet to be determined, we can be sure they will come into play in one form or another. How we react to range shifts and categorize species movements is a matter of human perception. Based on our values, we consider new species that come into our region as invaders, valuable treasures, or something inconsequential to be ignored.

Changes in the water

As a result of human-caused climate change, our oceans are in the process of becoming warmer, more acidic, and less able to carry oxygen. To remain in habitats that match their required conditions for survival, some marine species are moving towards the poles or into deeper waters. Affecting everything from kelp to clams, these range shifts are predicted to continue and have implications for fisheries as well as ecosystems.

In the Salish Sea, southern marine species are making their way into our temperate waters. For example, Pacific white-sided dolphins are becoming more common, while simultaneously disappearing at the southern extent of their range in the Gulf of California. Local populations of Pacific herring, prey for Pacific white-sided dolphins, are already struggling without contending with additional predators. While seeing any marine mammal may be exciting, the consequences of new players in local food chains are unknown.

Pacific white-sided dolphin sightings are increasing in local waters, while at the same time these animals are disappearing from the Gulf of California. Range shifts like this will have consequences for food webs. Photo: NOAA Fisheries West Coast.

Changes on the land

For Mayne Island’s terrestrial ecosystems, increasing severity of summer drought is the most obvious impact of climate change. Increased frequency of heavy rainfall and overall increase in annual rainfall also significantly affect the areas in which specific plants can grow. For example, western red cedar has suffered in recent years from changing rainfall patterns. At the drier edge of its suitable habitat, many individuals have been killed by drought, and at the wettest edge of its habitat individuals are being killed by prolonged flooding. Douglas fir, arbutus, and Garry oak are more drought tolerant species that may replace western red cedar in drier sites, while in wetter valley bottoms Pacific willow and other flood-tolerant shrubs may increase in abundance.

In the Southern Gulf Islands, a significant barrier limiting movement of native plants into new microclimates is deer overpopulation. For example, seedlings for tree and shrub species that would replace western red cedar are eaten before they can establish. In this way, deer overpopulation greatly reduces the ability of terrestrial ecosystems on Mayne Island to adapt to climate change.

Deer overpopulation is a significant barrier to plant establishment and dispersal to new areas. Photo: Daniel Lintott.

Why encourage native species to flourish?

At the Conservancy, we often field questions about how landholders can best adapt to and prepare for a changing climate. Sometimes, people wonder if they should plant species from southern ecosystems to account for our now drier summers. We caution against this idea. Living things require a combination of environmental and biological factors to be healthy and thrive, with temperature and precipitation being only two of many influences on survivorship. Accelerating range shifts runs the risk of losing the natural resilience of our native species, in addition to losing global biodiversity.

The native plants and animals we have in the southern Gulf Islands have spent thousands of years adapting to this specific area and interacting with one another. Each has an important role to play in local food webs, and the loss of one component of the food web can cause the rest to unravel. For example, many insects have specialized to eat specific types of plants. If those plants are lost from an area, those insects that form a crucial base in the food web are lost as well, impacting food availability for other life forms tied into the web.

The Southern Resident Killer Whales are a famous example of animals that have specialized to eat only one specific food source: Chinook salmon. Photo: NOAA Fisheries West Coast.

Additionally, genetic variation is important to help sustain species and maintain ecosystem functions through climate change, as individuals with different genes can survive in different conditions. As island populations, Mayne’s native species help contribute to variation in a larger gene pool.

How can we help local ecosystems thrive in a changing climate?

Climate change creates challenges for local species and ecosystems that highlight the need for specific nature conservation strategies. One such strategy is to focus conservation and habitat restoration efforts strategically to create wildlife corridors, improve connections between remaining habitats, and reduce habitat fragmentation. Drastically reducing deer populations in the Southern Gulf Islands, and particularly on Mayne Island where exotic European fallow deer have been introduced, will be critical if terrestrial ecosystems are to successfully adapt to a changing climate. Having baseline data is imperative for identifying range shifts, understanding local ecosystem impacts, and informing management decisions accordingly.  

We encourage people to grow native species and to help them survive: make sure you’re planting water-loving species in a wet area, put up deer fences to help plants establish properly so they’re better suited to surviving drought. On a larger scale, we can help reduce the impacts of climate change by preventing deforestation, restoring and conserving intact habitats, reducing our emissions, and using resources more sustainably.

The Conservancy’s restoration project at the Hedgerow Farms wetland is one example where we’re practicing our own restoration advice: Look close and you’ll see the deer exclusion fence and the water-loving native seedlings planted in wet areas where they have the best chance of survival.

Further Reading

The importance of baseline data.

Updates on Mayne Island’s deer issue.


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