by: Daniel Frasca | February 22, 2023

Every road paved through a forest causes habitat fragmentation.

The resources necessary to sustain an ever-increasing human population have placed an unprecedented burden on the world’s biodiversity. Satellite imagery of our planet reveals the devastating effects human development has imposed on the natural world. Our blue and green planet is becoming a mosaic of disappearing ecosystems, each a semblance of the natural habitat that once was. Roads, crop fields, and other human impositions permeate the natural world, creating small segments of habitat where a lucky few species remain. The process whereby large swathes of contiguous habitat are segmented into smaller “islands” of lower-quality ecosystems is called habitat fragmentation.

The Drivers of Habitat Fragmentation

Habitat fragmentation is occurring at an alarming rate across the globe. While natural events such as volcanic eruptions and fires can fragment habitats, the primary driver of habitat fragmentation today is human development.  Every road paved through a forest or fenceline driven across a grassland is a perpetrator of habitat fragmentation. Each incursion imposes an artificial edge within the natural habitat that came before. A recent study illustrates the sheer scale on which habitat fragmentation is occurring, estimating that 70% of the world’s remaining forests are within one kilometer of the forest’s edge. [1]

Songbirds are an example of an edge species that have adapted to survive on the forest’s edge.

The Impacts of Habitat Fragmentation

An ecosystem is a fragile complexity that depends on the existence of each individual organism residing within the system. Seemingly isolated individuals and functions are interwoven components of a much larger system, intricately strung together like a spiderweb. An ecosystem is truly a whole greater than the sum of its parts, with each individual organism performing a function critical to the existence of the interwoven system. When contiguous habitat is divided into smaller fragments, the integrity of the entire system is compromised. The remaining patches of habitat will not be able to recreate the complexity of the larger system it was once a part of.

Fragmented landscapes alter ecosystem dynamics to favor the survival of certain species over others. So-called “edge species” have adapted to survive in the boundary areas between ecosystems, also known as ecotones. Songbirds are one such example. Nesting in the trees of the forest while feeding in the open lawns of our backyards, the songbird’s survival depends on the presence of a forest edge. Edge species tend to have much higher population densities in the ecotone in comparison to the interior of the habitat, a phenomenon known as the edge effect. While these species have evolved to survive in the transitional boundary zones where two ecosystems collide, other species are specifically adapted to the conditions of the interior habitat. Habitat fragmentation creates edges that expose “interior species” to edge conditions for which they are not well adapted. Therefore, the process of habitat fragmentation favors the survival of edge species at the expense of the species adapted to the habitat interior.

Habitat fragmentation will accelerate the trend toward species extinction by limiting wildlife mobility. Many animal species rely on annual migrations to ensure reproduction and survival. Degraded and fragmented landscapes act as barriers along these routes and impede these cyclical migratory patterns, which are fundamental to that species’ survival. Interfering with these fundamental life-cycle behaviors increases the likelihood of a species’ extirpation and extinction. Entire populations are effectively restricted to a small “island” of their original habitat. This isolation also interferes with the evolutionary process on a genetic level. A loss of genetic diversity tends to arise in small populations and can impair a species’ ability to adapt to changing conditions. Reduced gene flow can limit the occurrence and spread of favorable traits. Finally, population size can change drastically when individual numbers are small due to natural fluctuations in birth and death rates. Fragmented landscapes and the resulting isolated populations mean species in fragmented habitats are more vulnerable to extirpation.

Fragmented landscapes create “islands” of isolated habitats.

Habitat Fragmentation and Climate Change

The natural world has showcased its spectacular ability to adapt and overcome time and time again. All life on Earth must once again adapt, this time compelled to react to a human-induced crisis. If history is any indicator, life will seek out the conditions in which it was adapted to survive. As the climate changes, entire ecosystems will migrate to more favorable regions on a global scale. Ecosystems will flee poleward to adapt to rising temperatures, starting from the equator. The polar regions will be the first victims of climate change as there will be nowhere to migrate to (hence why the polar bear has become the poster species of climate change). The tundra, which currently encircles the polar region, will migrate to replace it, while the taiga forest will replace the tundra, and so on. This will also happen in mountain ecosystems, where the tree line will migrate upslope as climatic conditions allow. Climate adaptation would unfold like this in a perfect and predictable world, but the world is far from perfect, and mother nature is notoriously unpredictable.

Wildlife corridors combat habitat fragmentation by reconnecting landscapes.

Humankind is compelling the natural world to adapt to a rapidly changing climate while simultaneously preventing it from doing just that. Fragmented landscapes impede the natural adaptive process of the world’s ecosystems. We must provide avenues for our precious biodiversity to pursue more favorable climatic conditions by designating areas for wildlife corridors. So-called wildlife corridors reconnect fragmented habitats and, when strategically placed, can facilitate climate adaptation by providing byways for climate migration. Landscape connectivity is our best asset in insulating biodiversity from the worst effects of climate change by enabling adaptive climate migration on a global scale.

The Anole Lizard is one of the many vulnerable species benefiting from ClimeCo’s wildlife corridor project in Colombia.

ClimeCo’s Partnership to Combat Habitat Fragmentation

ClimeCo has partnered with Saving Nature and UPROAR, global leaders in biodiversity conservation, to plant strategic wildlife corridors in biodiversity hotspots worldwide. Biodiversity hotspots are regions and ecosystems containing endemic species that exist nowhere else on Earth. In collaboration with a local non-profit, Bioconservancy Foundation, we are undertaking reforestation projects in the unique cloud forest habitat of the Colombian Andes mountains. The project’s first phase will restore over 550 hectares (~1350 acres) to serve as a wildlife corridor for many endangered species, including 30 IUCN-threatened bird species. Many new species have been discovered within the project area, including nine frog species, six lizard species, and seven orchid species. The olinguito, the first carnivore species discovered in the American continents since 1978, can also be found within the project area. The project is strategically located between two existing nature reserves which will serve as a large swathe of contiguous habitat to support and protect this critical biodiversity. With this reforested habitat, these species will be able to migrate upslope in response to the changing climate. This restored habitat connectivity enables landscape-scale climate resiliency and ultimately slows the alarming trends of species extinction in these biodiversity hotspots.

Creating favorable migratory conditions will be especially important in the 21st century as the entire Earth adapts to the rapidly changing climate. Reversing the trends of habitat fragmentation and ensuring landscape connectivity will slow the rate of species extinction and give our natural world a fighting chance at survival. We have a moral imperative to protect the globe’s biodiversity from a problem of our own making.

[1] Habitat fragmentation and its lasting impact on Earth’s ecosystems | Science Advances

About the Author

Daniel Frasca is a Program Development Associate working within the Nature-Based Solutions team at ClimeCo. Daniel is dedicated to developing ClimeCo’s diverse portfolio of nature-based solutions projects that produce tangible benefits for local communities and biodiversity.