The story of Coastal Douglas-fir forests: Protect and connect

Connectivity is vitally important at all sorts of scales over time and space.

Connectivity is the linkage of habitats, species, communities, and ecological processes at multiple spatial and temporal scales. Connected places provide species with access to critical habitat for feeding, shelter, and breeding while also allowing nutrients, water and energy to flow across the landscape. According to Dr. Pamela Wright, the maintenance of connectivity is essential for protecting biodiversity and all the ecological processes that are necessary for life on this planet.

Defining connectivity

Connectivity exists in multiple dimensions. It happens horizontally and vertically; from low to high elevations, along ridgelines, across landscapes, and between habitat types. It also happens over time. 

An overhead view of where the ocean meets forested land.
Connectivity could also be defined as the uninterrupted confluence of multiple habitat types. Photo by Alex Harris.

At the spatial scale, connectivity is typically described in geographic terms, or laterally, meaning movement from point A to point B. Something that is often overlooked in this definition however, is vertical movement. Some species have requirements for life that require them to move up and down in vertical space, making daily migrations from the forest canopy to the forest floor and back again, while others have subterranean movements that are equally important. Though Pacific chorus frogs (Pseudacris regilla), for example, are typically ground-dwellers, moving between wetlands and low vegetation on the forest floor, they are capable of climbing up into trees to search for food and evade predators.

A small green frog holding onto the bark of a tree.
Pacific chorus frog (also known as the Pacific tree frog). Photo by Alex Harris.

At the temporal scale connectivity considers both 1) shorter-term daily or seasonal migrations and 2) longer-term movements, such as those taken to adjust to changing climates. 

Ecological connectivity is the unimpeded movement of species and the flow of natural processes like water, energy, nutrients, and natural disturbances that refresh and regenerate ecosystems across a land- or marine-scape at all spatial and temporal scales.

Dr. Pam Wright

Olive-sided flycatchers (Contopus cooperi), for example, are small forest-dwelling birds that make daily movements to areas where there are, as their name suggests, flies and other insects to eat. Those insects tend to be most abundant in wet areas, like lakes, ponds, and marshlands. This means that the flycatcher is probably moving from interior forest to wetter areas daily. These frequent movements are important. Without connectivity between those two habitat types, the flycatcher would not be able to meet its daily food and shelter requirements.

An olive-sided flycatcher sitting at the top of a tree.
Olive-sided flycatcher. Photo by David Bell.

Rough-skinned newts (Taricha granulosa) make seasonal movements. Twice a year they migrate from forests where they overwinter in the soil to keep warm,  to water bodies where they reproduce. The coming of the rain is typically the signal for them to head back to the forest in the fall. These seasonal movements are vital to their reproductive success. Upscaling this to bigger-bodied species like caribou and wolves, movements occur over very large geographies, hundreds of kilometers in scale. Movement between one population to another allows genetic material to flow between them. Without this exchange, populations become increasingly small, isolated, and genetically fragile. Further, unexpected disturbances, like an avalanche or other natural disaster could decimate a population entirely.

A newt on the forest floor.
Rough-skinned newt. Photo by Alex Harris.

Though animal movement across the landscape is easily observable, plant migration may be less  noticeable. Though individual trees and other plants do not move once established, seed dispersal is vital to many plant species’ adaptive capacity. That is, when a plant’s seed disperses and germinates in a new place, that new offspring must adapt to slightly different conditions than those experienced by their parent plant(s) in order to survive. 

Some species have seeds that have evolved for easy wind dispersal, like the winged samaras of maple (Acer) species that resemble tiny helicopters. Other species require external vectors of transport. Take a coastal Douglas-fir tree (Pseudotsuga menziesii spp. menziesii) as an example. Typically their seeds do not fall far from the parent plant, but animals like squirrels and birds will pick seeds from the Doug-fir cones and transport them farther away than would have been possible otherwise. Other species, like common burdock (Arctium minus) which has been introduced to British Columbia, produce barbed seeds that easily stick to animal fur and clothing for transport.

Seeds on a big leaf maple tree.
Big-leaf maple (Acer macrophylla) samara. Photo by Alex Harris.
Cones on a douglas-fir tree.
Douglas-fir cone. Photo by Alex Harris.

Plants may move small distances each reproductive cycle, but over time they make notable moves and must find their way to suitable habitat if they are to establish and survive. This is an increasingly important consideration as climate change impacts become more ingrained in seasonal cycles. For example, a tree like red alder (Alnus rubra) thrives in moist to wet environments. If surrounded entirely by dry upland sites, alder occurrence will be limited to small pockets in those areas over time. If those habitats stay drier longer or grow in size due to human interference (e.g., construction of a ditch draining a site) or climate change, red alder may not regenerate in those areas. 

Plants, like animals, require adequate connectivity to maintain healthy genetic flow. Without it populations can lose genetic fitness over time and experience the same vulnerability to change as animal species. This not only puts populations at risk, but on a larger scale can significantly reduce local biodiversity. 

A forest with green vegetation, moss covered downed logs, and trees.
Alder and western redcedar (Thuja plicata) grove. Photo by Alex Harris.

The value of connectivity on the landscape: Benefits to local ecologies

In addition to being essential to newts, flycatchers, caribou, red alder, and all terrestrial species at all scales, it is important to think about connectivity from an ecological process perspective. In addition to genetic flow, this includes hydrologic connectivity from the upper branches of a watershed all the way down to its outflow. A good representation of this significance is the movement of anadromous fish species, like salmon and steelhead trout (Oncorhynchus mykiss irideus), who begin their lives in freshwater streams and migrate to marine environments to grow and mature before returning to their natal habitat to reproduce and die. Again, this is a species-based example, but beyond the facilitation of migration and genetic exchange, these interconnected waterways drive hydrological recharge throughout entire ecosystems.

A small stream running through the forest.
Hydrologic connectivity is an essential component of intact ecosystems. Photo by Alex Harris.

Analysis has shown that even the biggest national parks in Canada are too small and too disconnected to adequately support the largest species that live within them.

The importance of connectivity really depends on what is being connected and who it is being connected for. For highly mobile species, such as birds, at small scales like on the Southern Gulf Islands, for example, connected parcels are probably less critical than more high quality core areas. For herptiles (i.e., amphibians like newts) and reptiles (e.g., frogs) habitats need to be good quality and connected, but because these species are less mobile compared to birds, the spatial scale can be smaller. In the case of wider-ranging terrestrial species, tons of well-connected habitat is essential. 

Connectivity breaks

A connectivity break occurs when movement through space is impeded by actual physical barriers or from risky environments, which can range from the presence of people, to loud noise, to light. However, like most things in ecology, the answer to “what defines a break in connectivity” is: it depends. A fully connected landscape would be completely permeable, allowing access across a landscape whenever and wherever a species might want to move. This level of permeability does not exist. Even if humans had never been, there are physical barriers like waterfalls, stream breaks, and rock walls that limit movement. The presence of predators, especially if they are persistent enough, can also cause breaks in connectivity through the ecology of fear.  However, humans inadvertentlyーand sometimes advertentlyーsever connectivity by building roads; compacting fine soils and thus restricting water flow and subterranean movement; cutting down trees; and other activities.

The severity of a break in connectivity is quantified by how frequently and how significantly it impedes movement. For a rough-skinned newt, a trail or roadway with even low traffic levels can be enough to break connectivity due to mortality effects such as being trampled, run over, or desiccating as they attempt to cross. 

An aerial view of a road with forest on both sides.
Roads are common connectivity breaks. Photo by Alex Harris.

Though connectivity breaks are typically overtly physical, like a roadway or house, threats to connectivity are also processes that fragment habitats like excessive herbivory. The Columbian black-tailed deer (Odocoileus hemionus columbianus), though native to the Southern Gulf Islands, are also hyperabundant due to carnivore extirpation and human development of environments that favour deer. As a result, deer are browsing out the regenerative potential of local landscapes. Invasive plant species are similar. Whether it is spurge laurel (Daphne laureola), broom (Cytisus scoparius) or others, these species are incredibly successful which is what makes them so invasive. They threaten connectivity by creating hostile landscapes that native species cannot adequately move through and further, do not provide the same necessities of life to local populations that native species do. 

A deer reaching up to munch on vegetation.
Columbian black-tailed deer are hyperabundant across the Southern Gulf Islands, creating challenges for maintaining healthy understories and connectivity. Photo by Alex Harris.

At a mechanistic level, climate change is also exacerbating and accelerating the size and severity of connectivity breaks. Increasing drought, unprecedented disturbance events like catastrophic wildfire and flooding events, and even changing human habitation patterns can all contribute to habitat fragmentation.

Mobilizing connectivity: Protection priority

Unfortunately, options for protection, particularly in the Coastal Douglas-fir zone where a majority of land is privately held, are limited. In an ideal world, systematic conservation approaches would safeguard broad landscapes and seascapes, creating an interconnected network of protected places. In reality, ecological protection in Canada has historically occurred in a patchwork of isolated areas.

To transform the reality into the ideal conservation scenario there are three requirements that must be met:

  1. Core areas with high levels of protection and treated as sacrosanct, such as a conservation easement or provincial or national park. Core areas should be large enough and have good enough quality habitat that they meet many life requisites for the species and processes intended for protection and be managed to favour conservation. 
  2. A connectivity matrix or the “fabric” between core areas. This consists of all areas outside of human infrastructure like buildings and roadways and ideally includes protected corridors, in addition to more “working landscapes” like agricultural fields.
  3. Permeability or a reduction of barriers. 

Taken together, this means core areas should be connected via a network of intact corridors while permeability of the surrounding matrix is maintained. 

A person pointing on a map that they are holding.
Connecting core areas should be a core motivator for protection. Photo by Alex Harris.

Unfortunately, it is rare that core areas, particularly in heavily occupied landscapes like the Southern Gulf Islands, are big enough to meet the life requisites for many species. In fact, analysis has shown that even the biggest national parks in Canada are too small and too disconnected to adequately support the largest species that live within them. Further, they are not representative of the country’s biodiversity hotspots. The same is true of provincial parks in BC. Though these protected areas are slowing the loss of biodiversity, they are not big or numerous enough; they are not always located in the right places; and they face too many internal and external threats to save species by themselves.

This raises the questions: where should conservation time and treasure be spent? On maintaining cores or corridors? The best answer is both. Simultaneously. It is not an either or situation. Core protected areas will not persist as refuges in the long run unless they are of sufficient size, well-designed, and connected. They also need to be in the right places, of the right shape and configuration, and properly managed to reduce threats and safeguard biodiversity. Because connectivity is multidimensional, planning for its maintenance requires a great deal of analysis and attention. One must consider all the important flows across the landscape. It is also important to consider issues of adjacency (e.g., activities occurring on neighboring properties) and whether a habitat will be at risk of degradation if left unprotected.

A rivers running through the forest right next to a large clearcut area.
Despite best intentions for the maintenance of habitat connectivity, adjacent land use can interrupt flow of species and processes across the landscape. Photo by Alex Harris.

As an example, imagine a core area is already protected and there is potential to protect another property nearby. In between there is a small-scale farm. While agricultural practice might decrease landscape permeability for some species, many will be able to navigate that pathway, allowing ecological processes to flow between the two adjacent properties. This could be a good connectivity neighbour. It is likely that the second parcel can be protected as a core area, without having to acquire the farm in between.

Of course, conservation efforts will always be influenced by local interests and conditions. If the goal in this case is to protect a rough-skinned newt population, both wetland and interior forest habitat not only need to be protected, but connected to accommodate seasonal migrations. Presence of an agricultural field between a waterbody and the forest could be  enough of a barrier to prevent newts from moving between required habitats. In this case, it might be worthwhile to spend the conservation dollars to acquire the intervening property and connect the wetland and the forest.

An aerial view of a body of water surrounded by forested hills.
Connectivity may best be defined at a local scale based on the species and habitats of interest. Photo by Alex Harris.

Data suggests that the current rate of extinction is occurring at a rate 100 times faster than what would be expected naturally.

Habitat fragmentation has been and continues to be the biggest threat to the loss of biodiversity globally. This is also true in Canada. There are several measures that exist to quantify this loss, one of which is the Living Planet Index (LPI). It measures the state of global biodiversity based on population trends of vertebrate species in a variety of habitat types, tracking over 5,000 species and 30,000 populations. According to the most recent LPI report, published in 2022, global wildlife populations have declined by 69% since 1970. This level of decline is so severe that many populations are at risk of becoming extirpated. Though these numbers are indicative of global trends, they also accurately represent the situation in Canada. 

Extirpated

Regionally extinct. On a cumulative scale, over time extirpations can lead to complete extinction.

The LPI for four national parks in Canada shows that even in some of the biggest protected areas in the country, some populations are still experiencing significant declines. This means that some of our strongest conservation tools are not working as well as they ought to be. That is because these protected areas are not big enough and the surrounding environments are too fragmented  to provide the requisites of life for local species. Further, there is often too much fragmentation within the largest protected areas. So they are being fragmented from the inside and the outside. Banff and Jasper, for example, are stunning and provide vital habitat but they are also riddled with human use. The same is true for smaller protected areas, whether they are national parks or smaller, locally managed areas. Though these places are inarguably incredibly valuable for human use, at present recreational uses often trump conservation objectives and can overwhelm ecological capacity.

A turquoise lake surrounded by snow capped mountains.
Banff National Park. Photo by Arleta Tyzo.
A snowy mountain towering over a road in Banff.
Though Banff is a vital protected area, it is also heavily impacted by human use. Photo by Arleta Tyzo.

Ultimately, the risk of fragmentation is continued mortality and plummeting biodiversity. There is a great mass extinction event underway right now, the 6th known to this planet but the first to be caused by the activities of one species: humans. Data suggests that the current rate of extinction is occurring at a rate 100 times faster than what would be expected naturally. If this is allowed to continue, the loss of biodiversity will be greater than the mass extinction event that led to the disappearance of dinosaurs. Yet, this often goes unnoticed by people. It is like the fable of the camel’s nose, in which a camel is allowed to stick their nose into a miller’s workspace. The camel tests the boundaries and slowly moves into the room until entirely inside and then refuses to leave. People are so in the middle of habitat fragmentation and climate change that we might not fully grasp what is happening until it is too late.

Key decision-making principles: Protecting the “right” places

With scarce energy and scarce resources available to support conservation at the scale needed, strategic planning is essential. That is, identifying conservation priorities within a specific geography and setting goals and objectives for safeguarding habitat, ecosystem processes, and species movement across that landscape. It is also essential to build relationships with landowners to adjust behaviors to make the landscape more permeable and thus support the maintenance of the conservation matrix. 

In planning, the general rules of thumb should be applied:

  • Bigger core areas are better than smaller ones.
  • Habitat quality should be prioritized over size.
    • That is, areas that have the highest habitat quality are better than size alone.
  • Circular-shaped core areas are better as they have less edge exposure.
  • The closer core areas are together, the better.
    • Proximity means they are more likely to serve as pathways of connectivity.
  • Connectivity is key.
  • Core areas should be  embedded in a high quality (i.e., well managed and permeable) matrix.
  • Replicate areas arrayed across environmental spectrums (e.g., latitude, elevation, geography, ect) to allow for change and as a risk management strategy.
    • That is, in the past areas were individually selected for protection, they were not thought of as a network across the landscape. If there was one protected area that was representative of a Coastal Douglas-fir forest that was considered enough. But change happens on landscapes naturally and due to human use. A forest fire, a hyperabundant deer population, or some other threat could overwhelm the forces of regeneration in an area, and if that is the only representative area of an entire ecosystem that is a huge loss. Maintaining replica or multiple areas that protect the same kind of general ecosystem provides potential to respond to those disturbance events.

In sum, big, circular, connected, and high quality habitat embedded within a matrix of permeability should be the goal. 

Local conditions matter. In places like the Gulf Islands, protection mostly occurs on very small acreages. This means that target conservation properties must be in good ecological condition or at least restorable within a reasonable timeframe. If the surrounding matrix to those target areas is in high contrast to conservation objectives (e.g., heavily developed) and the features or species the land is being set aside to conserve are particularly sensitive to development/edge effects then expanding the area of formal protection should be a priority. Conversely, in areas like rural Saanich where a significant portion of the greenbelt is within the Agricultural Land Reserve, liaising with property holders to increase landscape permeability may be a higher priority than outright land acquisition.

A creek with both trees and newly planted vegetation around it.
The Galiano Conservancy Association has been working toward conserving habitat and restoring it, contributing to strengthening the local connectivity matrix. Photo of the Chrystal Creek watershed restoration project. Photo by Alex Harris.

What are your key recommendations for improving the way we connect habitats in the CDF?

For conservation organizations (governmental or non-governmental)

Have a good plan. Build understanding of how the landscape works, how to support connectivity, and what the risks are to the protection process whether ecological, social, or political. Use that understanding to prioritize areas for protection and always monitor results.

For decision-makers

Like conservation organizations, it is essential for decision-makers to adequately plan to support the maintenance of connectivity and the expansion of core protected areas within their jurisdictions. An obvious way to do this is to limit urban sprawl into natural areas. Supporting land protection initiatives at all scales through funding  is another pathway to protecting connectivity.

For homeowners

While land trusts and decision-makers are big players in protecting core areas, all onus cannot be put on them to provide all the protection needed to maintain biodiversity. It is important to recognize that those who live, work, and travel in the matrix are absolutely critical for ecosystem survival. It is the responsibility of landholders to consider:

  1. What can I do to make my piece of property more permeable to the movement of species and ecosystem processes?
  2. What have I been doing that might be making my property a more hostile environment? 
  3. Which of those things can I change? 
An aerial view of the shoreline where the ocean meets fragmented forested land.
The decisions made by landowners can significantly alter connectivity on the landscape. Photo by Alex Harris.

One simple change is to establish, or reestablish as the case may be, vertical complexity by maintaining overstory trees and planting midstory shrubs. These are landscape elements that often get removed because they can block long range views, but by maintaining them short range views vastly improve with the appearance of birds, pollinators and other species. Another change  is to green pathways, rather than using asphalt, concrete, or gravel, which would  make it easier for amphibians and reptiles to move across. Finally, removing invasive plant species and replacing them with native ones can help to restore connectivity while also enhancing local biodiversity.

Further reading and references

Hilty, J., Worboys, G. L., Keeley, A., Woodley, S., Lausche, B., Locke, H., … & Tabor, G. M. (2020). Guidelines for conserving connectivity through ecological networks and corridors. Best practice protected area Guidelines Series, 30, p-122. Available to download at: https://portals.iucn.org/library/node/49061

Hilty, J. A., Lidicker Jr, W. Z., & Merenlender, A. M. (2012). Corridor ecology: the science and practice of linking landscapes for biodiversity conservation. Island press.

Lemieux, Christopher J., Aerin L. Jacob, and Paul A. Gray. 2021. Implementing Connectivity Conservation in Canada. Canadian Council on Ecological Areas (CCEA) Occasional Paper No. 22. Canadian Council on Ecological Areas, Wilfrid Laurier University, Waterloo, Ontario, Canada. vi + 216 pp. Available to download at: https://scholars.wlu.ca/cgi/viewcontent.cgi?article=1044&context=geog_faculty

About Dr. Pamela Wright

Pam is a retired professor of conservation science from the Ecosystem Science and Management program at the University of Northern British Columbia. Her research and teaching focused on applied conservation-based approaches to protected areas design planning and management; managing and monitoring the ecological integrity of protected areas; and evaluating the effectiveness of management. In the last decade, she focused on developing and applying approaches for climate-conscious systematic conservation planning in British Columbia. She worked collaboratively with government and non-government organizations and Indigenous governments to undertake this work. She now lives on the SGI where she paddles, gardens, and volunteers at her local conservancy as well as the Yellowstone to Yukon Conservation Initiative.

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Research scientist, Adam Warner conducting genetics research in our genetics lab.
Photo by Alex Harris / Raincoast Conservation Foundation.