It stands to reason that as the climate warms, species will shift poleward, northward in the northern hemisphere and southward in the southern hemisphere, to stay within their comfortable temperature ranges. This premise inspired many of the large wildlife corridors designed over recent decades: vast networks of protected areas connecting natural habitats from north to south to help species move toward cooler latitudes.
However, scientific research is beginning to shift that paradigm. For many animals and plants, escaping rising heat does not require travelling hundreds or thousands of kilometres. Climbing a mountain is often enough.
Altitudinal or vertical corridors could prove to be among the most effective tools for helping biodiversity adapt to global warming. Initial mapping across the Amazon and the Andes, alongside ecological connectivity and restoration projects in regions like Yellowstone, Costa Rica, and Patagonia, shows that for many species, the future lies not further north, but higher up.
In this article:
- When climbing is easier than migrating
- Mountains as climate refuges
- An unprecedented map for the Amazon
- Is there enough room at the top?
- What happens when the mountain runs out?
- A race against time
- The Patagonia example
- The Yellowstone and Yukon example
- The Costa Rica example
- 21st-century infrastructure can also be green
A rise of just a couple of degrees in average temperature might seem minor, yet it can transform an ecosystem entirely. A temperate forest may cease to offer suitable conditions for certain birds; an amphibian may find traditional breeding pools too warm; an orchid may lose the humidity essential for its survival. In such cases, species face two choices to avoid extinction: adapt to the new climate or move elsewhere.
For years, it was assumed that this movement would primarily follow horizontal paths toward cooler latitudes. Over the last two decades, however, numerous studies have confirmed that species in mountainous regions often adopt a far more efficient strategy: heading uphill.
At first glance, this might seem counterintuitive. Climbing a mountain brings you slightly closer to the sun, so shouldn’t it be warmer? In fact, the opposite is true. Air is not warmed directly by solar rays, but primarily through heat absorbed by the Earth’s surface and radiated back into the atmosphere. As we climb, we move further from this primary heat source into thinner, less dense air that retains less energy. As a result, temperature drops with altitude at an average rate of 6.5 °C for every 1,000 metres of ascent, depending on local weather conditions. This gradient turns mountains into genuine climate refuges, enabling species to escape global warming without travelling long distances. It provides a shorter, faster, and often far more viable escape route.
This pattern is particularly evident in tropical regions, where species are adapted to narrow thermal ranges.
This shift is already well underway. Across the European Alps, the Rocky Mountains, the Andes, the Himalayas, and the tropical ranges of Africa, researchers have documented birds, mammals, insects, plants, and even freshwater fish steadily shifting their ranges toward higher elevations. This pattern is particularly evident in tropical regions, where species are adapted to narrow thermal ranges and possess little physiological leeway to withstand warming.
Mountains represent complex climatic mosaics. Across just a few vertical kilometres, they compress environmental gradients that would otherwise span hundreds of kilometres across flat ground.
While a valley floor might be dominated by warm conditions, cooler temperate forests appear just a few contours higher, followed by alpine meadows, and ultimately summits with temperatures akin to far higher latitudes. For biodiversity, these bioclimatic life zones, first detailed by Alexander von Humboldt, serve as vital migratory escape routes. Similar movements have occurred repeatedly throughout the history of the Earth during natural cycles of climate cooling and warming. The key difference today is that we are driving this shift, and warming is outpacing the rate at which most species can adapt.
Consequently, simply connecting existing protected areas horizontally is no longer enough. Ecological continuity must extend seamlessly from lowlands to peaks, allowing wildlife to shift gradually as they track suitable climatic conditions. Conservation planning must therefore expand beyond two dimensions, north to south or east to west, to integrate elevation as a critical third axis.
The Western Amazon is considered one of the planet’s primary biodiversity reservoirs. Here, the world’s largest rainforest meets the Andes mountain range, forming a massive natural gradient connecting lowland Amazonian forests to peaks exceeding 6,000 metres. Over millions of years, this transition has allowed thousands of species to diversify and adapt to vastly different temperature and moisture conditions. Under present climatic shifts, this gradient offers an essential route for adaptation.
An international research team has taken a key step forward by publishing the first regional map of altitudinal corridors across the Amazon. Published in the scientific journal Global Ecology and Conservation, the study identifies natural pathways maintaining connectivity between the Amazon lowlands and the Andean ranges. This connectivity is vital for enabling species to seek out cooler temperatures as global averages rise.
The research assessed millions of hectares across multiple Amazonian nations, evaluating where intact habitat remains continuous enough to allow viable species movement from lowlands into high-elevation Andean zones.
This dramatic elevation gradient makes the Andes one of the largest living laboratories for studying how biodiversity responds to climate change.
Spanning more than 7,000 kilometres, the world’s longest tropical mountain range links some of the planet’s most biodiverse ecosystems, including lowland rainforests, montane forests, cloud forests, high-altitude páramos, and alpine peaks. Every few hundred metres of ascent reveals shifts in landscape, species composition, and microclimate. This dramatic elevation gradient makes the Andes one of the largest living laboratories for studying how biodiversity responds to climate change.
The good news is that most of these vertical corridors remain intact. Unlike many other global regions, continuous forest tracts still rise uninterrupted from the Amazon basin into Andean cloud forests and alpine heights. This unbroken connectivity represents an exceptional opportunity to support species adaptation.
However, it also exposes critical vulnerabilities. Agricultural expansion, mining, road construction, energy infrastructure, and deforestation are increasingly fragmenting these high-altitude corridors. If these unbroken pathways are severed, many species will lose the chance to continue their upward climb.
This question is drawing growing concern and quantitative research across the scientific community. Because land area naturally decreases toward mountain summits, ecologists observe a clear pattern of biodiversity compression, with species crowding into progressively tighter physical boundaries.
It is like an apartment building where the residents of every floor are forced to relocate upward simultaneously. As long as higher floors remain vacant, the building can accommodate the pressure. The crisis emerges at the top floor, where high-elevation specialists have nowhere left to go.
Available territory shrinks, intensifying competition for food, shelter, and breeding sites, while disrupting established dynamics among predators, prey, plants, and pollinators.
On narrow summits, this spatial crunch creates an acute “ecological bottleneck.” Communities that evolved independently over millennia begin overlapping and competing, while specialized mountaintop endemics face severe habitat loss.
Ascending a mountain reaches an absolute physical ceiling. Mid-elevation species may continue moving upward for decades, but species already native to summit zones possess virtually no headroom. They remain stranded on shrinking “climatic islands”, increasingly crowded and unable to climb any further.
Researchers refer to this phenomenon as the “summit trap” or, more graphically, the “escalator to extinction.” As warming pushes species upward, they eventually reach the physical apex of the terrain. Beyond that point, any further temperature increase leads directly to sharp population declines or local extinction.
Early warning signs are already visible across multiple mountain ranges globally. Numerous alpine plant species occupy higher elevations today than they did just a few decades ago. Several montane small mammals and amphibians display increasingly restricted ranges, while specific insect and bird communities are abandoning breeding zones held stably for centuries. For instance, the distribution of the delicate Nevada grayling butterfly (Pseudochazara williamsi) in the Sierra Nevada is shifting higher each year, tracking climatic conditions no longer found lower down.
This pattern is also impacting mountain river networks across the Iberian Peninsula. In the Guadarrama National Park, brown trout (Salmo trutta) are shifting their spawning grounds toward higher, colder, and more oxygenated stretches of rivers like the Lozoya to ensure egg and fry survival. However, headwater channels offer limited length and volume. As fish migrate upstream, available spawning habitat steadily diminishes, culminating in an aquatic cul-de-sac.
Global temperatures continue to rise alongside more frequent, intense, and sustained extreme heatwaves, altering the planetary climate at a pace unmatched in recent history. While nature has historically adjusted to climatic shifts across centuries or even millennia, many species now face warming rates that far outpace their natural rates of evolutionary adaptation and dispersal. Finding a rapid route to cooler environments has become an immediate requirement for survival.
This mismatch presents a serious conservation challenge. If temperatures rise faster than species can migrate, even well-conserved corridors may prove insufficient to avert biodiversity loss. Acting before existing pathways are broken is therefore critical. While restoring a native forest can take decades, repairing a fragmented landscape is considerably more complex than safeguarding one that remains continuous.
Fortunately, many of these natural climate highways remain intact. Conservationists and land managers now have better data to locate, map, and protect them.
One of the most inspiring models of this landscape-scale conservation approach is located in southern South America. Over recent decades, Kris Tompkins, the largest individual land donor for conservation in history, alongside the team at Tompkins Conservation, has driven the world’s most extensive ecological restoration effort, contributing to the creation and expansion of national parks across Chile and Argentina covering millions of hectares. Journalist Amaro Gómez-Pablos, working on a collaborative project with ACCIONA, interviewed Kris Tompkins about this long-term vision, detailing the initiative in a powerful article.
The overarching goal was never solely to protect iconic species like the puma, huemul deer, or Andean condor, but to restore complete ecosystem functionality. This model focuses on rehabilitating native forests and wetlands, dismantling obsolete infrastructure, reintroducing extirpated species, and restoring contiguous landscapes capable of functioning as resilient, self-sustaining living systems.
These initiatives demonstrate how rewilding can serve as a powerful tool for climate change adaptation.
Although many of these initiatives began before climate adaptation became central to global policy, they clearly illustrate how rewilding supports resilience under warming scenarios. A restored, connected landscape offers species diverse microclimates and elevation ranges to seek refuge as conditions shift, providing a practical, nature-based approach to preparing ecosystems for the future.
One of the best examples of this new “altitudinal” philosophy is the Yellowstone to Yukon Conservation Initiative (Y2Y). Established in the 1990s, the project maintains an interconnected corridor spanning more than 3,000 kilometres from Yellowstone National Park in the United States through the Rocky Mountains to the Yukon territory in Canada.
Its initial objective was to secure safe passage for wide-ranging mammals—including grizzly bears, wolves, cougars, wolverines, and elk—by preventing roads, urban sprawl, and resource extraction from fragmenting core habitats. Over time, climate change has underscored the strategic value of this high-elevation corridor.
The uninterrupted spine of the Rocky Mountains allows wildlife to shift gradually across both elevation and latitude toward suitable climatic conditions.
The uninterrupted spine of the Rocky Mountains allows wildlife to shift gradually across both elevation and latitude toward suitable climatic conditions. Concurrently, constructing wildlife crossings, removing movement barriers, and expanding protected areas are establishing this corridor as genuine infrastructure for climate adaptation.
Another key project demonstrating this approach operates across Costa Rica and Panama. The AmistOsa Biological Corridor connects lowland rainforests in the Osa Peninsula and Corcovado National Park near sea level with La Amistad International Park, a UNESCO World Heritage Site protecting some of Central America’s most biodiverse mountain ranges, including Cerro Chirripó (3,821 metres), the highest peak in Costa Rica.
Across this vertical belt, ecosystems transition through a rich elevational gradient. While established primarily to counter deforestation and facilitate movements of umbrella species like the jaguar, Baird’s tapir, and scarlet macaw, the corridor serves as a critical climate adaptation asset. Maintaining uninterrupted connectivity across diverse elevations enables flora and fauna to shift gradually into cooler highland forests without encountering barriers such as highways, agricultural clearing, or urban sprawl.
It stands as a clear example of how ecological planning and regional land management can, and must, advance together.
Wildlife corridors represent infrastructure as vital as rail networks, highways, or power grids. Rather than transporting goods or passengers, they facilitate the movement of life. Integrating habitat connectivity into spatial planning from the outset has become an essential requirement for sustainable development. Beyond protecting static habitats, conservation must safeguard the movement pathways that allow species to endure.
Regional mapping across the Amazon and the Andes shows that functional corridors linking lowlands, cloud forests, and alpine summits still exist. Initiatives such as Yellowstone to Yukon, the biological corridors of Costa Rica, and the large-scale rewilding led by Kris Tompkins prove that this vision is already being actively deployed on the ground.
Building wildlife crossings over transport corridors, preventing infrastructure from severing key migration routes, restoring degraded native forests, adopting regenerative agriculture, and rehabilitating river basins improve biodiversity while strengthening ecosystem resilience against climate extremes. They are infrastructure solutions that are increasingly sustainable and less invasive, benefiting not only flora and fauna. If it is good for them, it is good for us; after all, we are nature too.
For many species, including our own, the path forward may no longer lie further north. It lies higher up.