Story | 21 Nov, 2023

Making Connections

Ecological corridors are crucial to connecting fragmented wildlife populations and habitats– and if implemented well can have social, economic and climate-related benefits too, finds Coreen Grant

Picture this: on the outskirts of the Los Angeles urban sprawl, a giant green overpass bridges a 10-lane freeway, flowing with heavy traffic. Up above, a mountain lion crosses the road, unseen. Countless cars stream past beneath as the apex predator moves undisturbed to the mountains on the far side of the freeway. 

This is the vision of the Wallis Annenberg Wildlife Crossing, a gigantic USD$87m bridge currently under construction in the Agoura Hills outside LA. Once completed, the bridge will be the largest wildlife crossing in the world. It is designed to allow animals such as the iconic LA cougars, with a host of other species from lizards to bobcats, to move unimpeded between habitats separated by the freeway.  

In a world where wild land and intact habitat is becoming increasingly fragmented, the creation of ecological corridors is a crucial – and growing – part of global conservation. 

The IUCN World Commission on Protected Areas’ Connectivity Conservation Specialist Group (CCSG) was established in 2016 to facilitate the emerging field of ecological connectivity. The group defines an ‘ecological corridor’ as any designated geographic space which is managed to support the interconnection of nature. This means corridors can range from structures like wildlife bridges to vast swathes of protected land or sea connecting important sites.  

Research shows that even under protection, areas of biodiversity cut off from others will slowly lose species and ecological processes. This is because the flow of genes between populations is blocked, making species less resilient to threats like disease, and unable to adapt to changing environments. 

Gary Tabor, Chair of the CCSG, explains that while protected areas such as national parks are vital for conservation, there is increased understanding that on their own, they are not enough. “We know once [an area] is designated, it’s not always effective,” he says. “If it’s isolated, it diminishes in ability to achieve its goals.”


Making space for primates

On the east coast of Brazil, the busy BR-101 highway cuts through fragments of coastal rainforest. Until recently, species were able to cross this road, but as traffic levels rose, the decision was made to double the highway’s width, rendering it impenetrable. The expansion was especially problematic for one species: the golden lion tamarin. Taking its name from the beautifully burnished colour of its fur, the tamarin is an endangered primate living only in Brazil’s Atlantic Forest. Although recovered from near extinction in the 1970s, tamarin numbers hover at around 3,000 individuals, making its entire population vulnerable. 

Significantly, the highway development isolated a small population of tamarins living in the Poço das Antas Biological Reserve. Recognising the danger this posed, a conservation association convinced the highway construction company to build an overpass. It was the first wildlife bridge built in Brazil: completed in 2020, its forested canopy now acts as an extension of the surrounding rainforest, providing a corridor through which tamarin populations can reconnect and spread.


Biological Cor, Members Mag 2 Roadside warning sign, Canada

Larger species can also benefit from corridor structures. Last December, the Southern Railway in India began constructing its first underpass for wild elephants, allowing the slow giants to move beneath rail lines, thus preventing collisions with trains. This August, surveillance cameras captured the first elephant using the completed underpass. Scientists believe that the dung he left behind will help fellow elephants recognise the underpass as a safe route.    

While individual structures can provide effective solutions for targeted species, landscape-scale corridor projects take a wider view of reconnecting entire ecosystems. Some countries have been leading the way for years: Bhutan established its first ecological corridors in 1999, and now over 51% of the country’s total land area is secured as protected areas and corridors. 

Meanwhile, the small but extremely biodiverse nation of Costa Rica has 44 formal corridors, representing around a third of its terrestrial territory. They are managed by the government in tandem with local committees, and some span the length of the country. The Barbilla-Destierro Jaguar Corridor, for example, links the southern Talamanca Mountains with the northern Central Volcanic Range. It also contributes to the larger Jaguar Corridor Initiative, a vast project aiming to connect jaguar populations from Mexico to Argentina, thus maintaining gene flow across the entire species range.

One of the largest projects in the world is the Yellowstone to Yukon Conservation Initiative, or Y2Y, a vast effort to create an interconnected system of wild lands and waters stretching along the Rocky Mountains, an area of 1.3 million square kilometres. By connecting swathes of habitat along this giant mountain corridor, the initiative aims to ensure that wide-ranging species such as grizzly bears, caribou and wolves have sufficient space to roam naturally, following prey movements and seasonal migrations.


Corridors for communities

It is not only wildlife that benefits from the creation of ecological corridors, however; local communities can reap the benefits too.  

On one level, there are economic opportunities. In northern Botswana, efforts to create safe corridors for elephants’ daily commute routes have resulted in an ‘elephant economy’, in which elephants act as an asset to local people, rather than a threat. Ecoexist, a conservation trust, pays farmers a premium price for their millet if they commit to protecting elephants. That millet is then used in a craft brewery catering to tourists, while a group called Living with Elephants performs traditional songs and dances.

The societal benefits of corridors extend beyond economics. Jodi Hilty, a leading expert on wildlife corridors and deputy chair of the CCSG, explains that corridors of intact habitat help to maintain basic ecological services, from flood mitigation to the prevention of zoonotic diseases. Within areas of intensive agriculture, corridors of wildflowers and hedgerows can be crucial for pollinating insects to reach farmers’ fields. 

On the Fijian island of Viti Levu, an inspiring initiative called Ridge to Reef works with Indigenous landowners to protect the island’s abundant natural resources, and therefore local people’s livelihoods. By creating a corridor of interlinked terrestrial and marine habitats, the project recognises the interconnected health of the island environment and takes a “‘whole systems’ approach to connectivity”, says Hilty.  

Working with people whose lives
are affected by the creation of corridors is key to their success, according to Alex Hearn, a marine fisheries ecologist.

Last year, Hearn was involved in the creation of the Hermandad Marine Reserve in Ecuador: an area of 60,000 square kilometres extending from the Galápagos to the Costa Rican border. It protects part of the Cocos-Galapagos Swimway, a narrow marine corridor used as a migratory route by critically endangered leatherback turtles and several species of shark.  

The success of the reserve is largely due to government collaboration with the fishing industry, according to Hearn. During its design, the Ecuadorian government undertook a consultation process to ensure that industry views were represented, with the result that fishing restrictions within the reserve were “respected from day one”. 

Ultimately, Hearn would like to see more coordination of conservation goals on a wider basis, across national borders. The Swimway corridor will only reach its full potential if Costa Rica decides to protect the section that falls within its territory. Otherwise, “what we’re doing is essentially shepherding these animals through to be caught on [fishing] long-lines as soon as they cross the border”, Hearn says. “That’s where we need more intercountry communication.” 

Time is running out for the type of global collaboration that Hearn envisages. As the world’s climate heats up and habitats change beyond recognition, species across the globe are struggling to adapt. But ecological connectivity can help ease this process, according to researchers.

If areas of habitat are well connected, species can migrate more easily: they can move north to follow colder weather patterns, for instance, or shift to higher altitudes.  

Recent research even suggests that corridors of restored habitat can help affect microclimates, with reforested corridors encouraging rain patterns to move inland to areas threatened by desertification. 

Seth Riley, a wildlife ecologist in LA, hopes that pioneering projects such as the Wallis Annenberg Wildlife Crossing can inspire similarly ambitious efforts to help species co-exist, even in the most urban environments. 

“Hopefully, [the crossing] is symbolic of what can be done, and the value of connectivity,” he reflects. Riley has been working on the project for over two decades, but says that ultimately, the bridge is “just the beginning” of what they hope to achieve.  

From animals on the brink of extinction to entire cross-border ecosystems, corridor projects are finding ways to help species connect. For Gary Tabor, connectivity will be the defining factor of conservation in the 21st century – if only we can realise its full potential. “In the future, we won’t be counting protected areas,” he says. “We will be counting how connected those areas are.”

Definitions from IUCN’s Connectivity Conservation Specialist Group 

Ecological connectivity: The unimpeded movement of species and the flow of natural processes that sustain life on Earth. 

Ecological corridor: A clearly defined geographical space that is governed and managed over
the long-term to conserve or restore effective ecological connectivity. Ecological corridors can be continuous or patchy (i.e. ‘stepping stones’).

Many other parts of IUCN also work on ecological corridors. Among these are:

•  IUCN Centre for Conservation Action
•  IUCN World Commission on Protected Areas’ 
    Transboundary Conservation Specialist Group

Recent and relevant IUCN resolutions:
•  WCC 2020 Res 014
•  WCC 2012 Res 152
•  WCC 2012 Res 146