Connectivity conservation

A wildlife overpass in Banff national park, in the Canadian Rockies. Photograph: Ross MacDonald/Banff National Park

by Jacqueline Oehri

Our world is a magnificent network of billions of living beings that are connected to each other and their environment. These connections occur geographically as species’ move through land- and seascapes. From species feeding upon others (like wolves preying on deer), to species engaging in beneficial partnerships such as the pollination of fruit trees by insects, or fungi and algae uniting to form lichens on the barks of trees, these movements and interactions create the web of life.

However, human activities, especially land-use change, are increasingly degrading ecosystems and habitats, which is disrupting the interactions between species. The transformation of natural ecosystems for agriculture, settlements and other human needs are among the main drivers behind the loss of connectivity

Science and policy are now working in tandem to protect and restore ecological connectivity. I am very grateful that as a postdoc in the labs of Drs. Andy Gonzalez and Brian Leung (McGill University), I have the chance to contribute to this work.

But exactly what is ecological connectivity, why do we care about it and what can we do to re-establish it? In this blog post, I answer these questions and highlight some of the fascinating and critical research we are conducting in the Gonzalez lab - from theory to practice!

So, what is ecological connectivity?

Ecological connectivity can be broadly defined as the ‘unimpeded movement of species and the flow of natural processes that sustain life on Earth’1.

Therefore, ecological connectivity describes the degree to which a species is capable of accessing and interacting with resources in its environment. So for example, how well a black bear can roam a landscape to find sites with blueberries, ants, and water, as well as how easily it can find sites to hibernate. 

Image designed by Kendra Hoff, CLLC, taken from Conservation Corridor.

To increase ecological connectivity in a landscape, ecological corridors (clearly defined geographical spaces that enable species movement) and ecological networks for conservation (a system of protected areas or other effective area-based conservation measures that are connected by ecological corridors) can be established2. As depicted in the image above, it is clear that ecological connectivity does not only exist on land but also in freshwater and marine environments. While it may not be obvious from the shore, research is showing that there are important movement routes in oceans too, check out this cool map of whale superhighways!

And why is connectivity important?

Connectivity and the movement of living beings are crucial for the long-term survival of individuals, populations, species and communities. For example, species need to move and forage to meet their daily needs of food and shelter. They also move to find mates for reproduction, to avoid predators or pathogens or to ‘track’ suitable climatic conditions (check this cool map of ‘migrations in motion’). Connectivity is essential to avoid inbreeding and therefore facilitates adaptation. Even more so, many species can only complete their life cycles by dispersing or migrating across landscapes and even continents. For example, monarch butterflies fly thousands of kilometers across North America from their breeding to overwintering locations in central Mexico, and sockeye salmon migrate from freshwater rivers, where they are born, to the ocean to feed and mature, only to go back to their natal stream to spawn.

Left: Monarch butterfly migration, credit: Sylvain Cordier/Gamma-Rapho/Getty images. Right: Sockeye salmon migration, Vancouver BC, credit: Vitya_maly/GoodFon.

Preserving connectivity for multiple species helps to maintain regional biodiversity and the species interactions that underpin the functioning of our ecosystems. For example, many trees and shrubs, such as mulberry, cranberry, and apple profit from seed dispersal by animals, such as the bohemian waxwing (Bombycilla garrulus) in North America. Also, a vast majority of flowering plants depend on pollinating insects such as the threatened yellow-banded bumble bee (Bombus terricola). For these functions (e.g. seed dispersal and pollination) to take place requires that both species populations can persist in the landscape and that individuals of each species can find and interact with one another. Finally, connectivity facilitates the provision of and access of people to ecosystem services (the benefits people receive from nature), such as pest regulation, recreation or cultural services. We are learning more and more about how ecological connectivity can contribute to the provision of these services, even though there are still many questions that remain unanswered.

Left: The Bohemian waxwing. Credit: Jorma Luhta/naturepl.com. Right: Yellow banded bumble bee. Credit: Wildlife Preservation Canada.

Human activities disrupt ecological connectivity

By now, we have transformed a very large fraction (~75%) of the ice-free land on the planet, mostly in warmer and wetter areas where we humans like to live. As a result, ‘wild’ areas are often only found in cold and dry regions, such as the Arctic or the Saharan desert. 

These land transformations generally come with the destruction of ecosystems and many species’ habitats, leading to so-called ‘habitat fragmentation’: the division of species’ habitats into smaller and more isolated fragments. For example, agricultural land is often composed of remnant fragments of forest left after it has been cleared to make way to grow crops or livestock. Also, built-up surfaces such as roads are often barriers to many species because collisions with vehicles cause mortality of small species, such as amphibians or reptiles, and large species, such as deer or moose.

Habitat fragmentation puts at least half a million species (about 10% of the world’s terrestrial species) at direct risk of extinction, via loss of habitat area, exposure to human disturbance, and consequent disruptions of ecological connectivity.

Left: Human land-transformations. Taken from Locke et al. 2019. Right: Habitat fragmentation. Taken from Haddad et al. 2015.

Towards actionable connectivity science

In theory it is quite clear that ecological connectivity is fundamental for biodiversity, ecosystem functions and therefore human existence, but in practice we continue to destroy habitats and disrupt ecological connectivity in many places. By restoring ecological connectivity in fragmented landscapes we can support a significant portion of biodiversity and ecosystem functioning, by effectively expanding the habitat available to species otherwise stranded in isolated habitat patches. 

So, it is high time for increased action on connectivity conservation. In my next post, I’m going to talk about how we, as a lab, are making connectivity science actionable and I will show you concrete examples of our efforts. In line with the UN Decade on Ecosystem Restoration let’s reconnect the web of life for our well-being and that of many other lives on our beautiful planet!