Making the Connection

Populations under pressure

Today humans are directly and indirectly transforming the Earth’s biosphere like never before. With urbanisation, industrial and agricultural activity, and infrastructure development exerting unprecedented pressure on global space and resources, the amount of habitat where wild nature can flourish is decreasing, compromising the ability of many species to survive. Wild animals are being cornered into smaller and smaller environments, with less room to migrate, disperse, reproduce, feed and generally thrive. Fragmentation of habitat is now one of the key drivers of the disappearance of species and the decline in species abundance (a process known as defaunation).

Our world is naturally highly inter-connected. National parks and other protected areas can greatly benefit biodiversity and the conservation of wild nature, but they often end up functioning as islands, where species populations are geographically and genetically isolated. This makes these populations far more susceptible to disease, climate change and natural disaster.

“Fragmentation of habitat typically results in isolated patches of nature,” explains René Henkens of the Wageningen Environmental Research department at Wageningen University in the Netherlands. “Populations of species in these patches are often small and simply not viable. The smaller the habitat, the smaller the population, the higher the risk of local extinction.”

Halting habitat fragmentation by conserving large intact landscapes and seascapes through the designation of more and larger protected areas or other effective conservation measures should, therefore, be a priority. But it may not be feasible in the short term, or even possible at the requisite scale.

The case for corridors

One established way of facilitating the exchange of individuals from isolated populations is to create corridors of protected habitat. These typically link larger protected areas, allowing species to move safely between them, thereby boosting overall population size and genetic flow and diversity.

This connectivity concept is central to the work being carried out in a number of Rewilding Europe’s operational areas. In the Central Apennines rewilding area in Italy, efforts to conserve and boost the Marsican brown bear population are focusing on the development of wildlife corridors between national parks, regional parks and biosphere reserves. In the Southern Carpathians rewilding area in Romania, Rewilding Europe and WWF Romania are working hard to ensure the connectivity and genetic diversity of reintroduced sub-populations of European bison. And in Western Iberia, Rewilding Europe is working with local partners to shape the Côa Valley through the development of a 120,000-hectare wildlife corridor – the Greater Côa Valley – that connects the Malcata mountain range in the south with the larger Douro Valley in the north.

Wildlife corridors come in an array of shapes and sizes, depending on the species of concern. They can range from hedges and fauna passages (such as a simple tube under a road) right through to expansive natural areas and “stepping stone” habitat patches that facilitate the migration of birds and sea turtles. The four corridors currently proposed for the Marsican brown bear in the Central Appenines rewilding area, for example, cover more than 40,000 hectares (400 square kilometres).

“If individual species have a connection problem, then you can develop highly species-specific corridors to solve local problems,” explains Henkens. “Corridors on a landscape scale, especially ecological networks, generally benefit a whole range of animals, although they may be developed with a flagship species in mind.”

Some species will happily take advantage of relatively narrow corridors, while others that are less accustomed to human presence will shy away from them. Many factors play a role in how attractive a wildlife corridor will be to animals: terrain type, vegetation cover, snow depth, topography, physical barriers of various kinds, and of course, human presence (including smells and noises).

Some of the most effective wildlife corridors enable animals to navigate single barriers. In the Canadian province of Alberta, for example, a lot of wildlife was historically killed while trying to cross the Trans-Canada Highway. A simple solution – a fence that kept wildlife away from the highway and funneled it towards a bridge – decreased road mortality considerably.

While the exact impact of wildlife crossings (or ecoducts) on the viability of animal populations has yet to be calculated, they have certainly allowed some species to expand their range and recolonise areas of habitat. This is the case with the LIFE+OZON project in Belgium, which has been a member of Rewilding Europe’s European Rewilding Network since the beginning of 2017. The reconnection of previously fragmented habitat here has seen populations of roe deer, red fox and wild boar all increase.

“There are many studies that prove that corridors work for the migration of species,” says Wageningen University’s Henkens. “Species have been observed again in areas where they were formerly extinct. Whether this can boost biodiversity by transforming non-viable populations into viable ones is mainly based on model simulations, and has yet to be proven through field studies.”

Scaling up

It is widely accepted that if wildlife is to really thrive and be robust enough to survive in the long-term, then habitats need to be connected to others via wildlife corridors. Connectivity conservation is now gaining recognition as an effective and timely way of counteracting many of the negative impacts of habitat fragmentation.

“There is overwhelming science, built on the theories of island biogeography and metapopulation dynamics, that connected habitats are more effective for saving species and ecological functions,” says Gary Tabor, director of the Montana-based Center for Large Landscape Conservation (CLLC). In this time of rapidly changing environmental conditions, connectivity is also viewed as a viable method for helping species adapt to climate change by moving from south to north.”

At its fifteenth meeting in Beijing in 2020, the 196 Parties to the Convention on Biological Diversity (CBD) are due to adopt a post-2020 global framework for biodiversity. There is hope among the conservation community that the goals of Aichi Target 11^* will be framed more ambitiously, with “50% for Nature” by the year 2050.

“Connecting fragmented landscapes and seascapes through ecological networks can effectively enhance the functionality of nature as the world grapples with more ambitious approaches to conservation,” says the CLLC’s Tabor.

“At present, 14.7% of land around the world is covered by protected areas, and only 7.5% of the world’s land is covered by protected areas that are connected,” he continues. “There is therefore significant potential for improving connectivity between these areas. If the world seeks large-scale conservation action rapidly, protected areas connected through ecological networks offer hope for wildlife.”

The world currently lacks a consistent approach to ecological connectivity implementation, with connectivity conservation facing its greatest challenges outside of protected areas. In Europe, the combined impact of habitat loss, a lack of connectivity and impaired ecological functioning is a major barrier to nature conservation, and hampers achievement of the goals laid out in the Birds and Habitats Directives and the Water Framework Directive.

Boosting ecosystem connectivity – by restoring and maintaining large, inter-connected areas of high quality habitat such as naturally functioning wetlands, floodplains, forests and grasslands – is therefore critically important to the future conservation of European nature.

“The current Natura 2000 network, which is a great asset for European conservation encompassing nearly 20% of the territory of EU member states, is missing a connectivity element,” says Rewilding Europe’s managing director Frans Schepers. “Going fowards it is therefore critical that we create a well functioning, large-scale green and blue infrastructure across the continent.”

Last year, Rewilding Europe, together with BirdLife Europe and Central Asia, the WWF European Policy Office, the European Environmental Bureau and the German Centre for Integrative Biodiversity Research, launched a three-year initiative entitled “Promoting and shaping the EU restoration agenda, including TEN-G, through mobilisation of rewilding principles to create a coherent ecological network in Europe”.

The aim of the initiative is to strengthen the EU’s restoration agenda, and to ensure that a coherent ecological network is created in Europe through the promotion and use of rewilding principles. Demonstrating that such principles are an efficient means of restoring European nature, those involved in the initiative will promote the acceptance of rewilding principles in political debate, and work towards their inclusion in the follow-up to the 2020 EU Biodiversity Strategy.

^*By 2020, at least 17% of terrestrial and inland water areas and 10% of coastal and marine areas, especially areas of particular importance for biodiversity and ecosystem services, are conserved through effectively and equitably managed, ecologically representative and well-connected systems of protected areas and other effective area-based conservation measures, and integrated into the wider landscape and seascape.