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A Better Connection for Refugee Plants

Software used to optimize flow for jets and phone calls adds a new wrinkle in protecting plants migrating due to climate change.
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When climate changes, plants don’t just sit there and take it. They pack up and move, seeking out new digs by migrating along climate “gradients.” During warming trends, they seek suitable habitat by moving either upslope to cooler altitudes or toward the poles (the South Pole in the Southern Hemisphere and the North Pole in the Northern Hemisphere). As the climate cools, they move downslope or toward the Equator.

Such climate-induced migrations were easier before several billion people — along with their farms, cities, roads, and other obstacles — took up residence on the planet, blocking migration routes and sometimes eliminating suitable habitat altogether.

For some time, ecologists and conservation managers have sought to help species overcome those obstacles by establishing “corridors” for migration. The operating principle is that if you know where a species is now and where its habitat will be as conditions change, you can establish protected corridors — a special lane, if you will — connecting the old range to the new.

But there are obstacles associated with corridors. They require substantial amounts of land, which may already be developed or be owned by someone who doesn’t want to sell it or allow a corridor on it. Acreage that is available may not be suitable habitat, even if the limited money for these projects is enough to acquire it. Also, with new range sometimes lying more than a hundred miles away, a species may not be able to migrate fast enough to outpace climate change.

It would be better if corridors required less area and species didn’t have to travel so far to reach new habitat.

A new method of computer modeling — developed by a team of scientists whose interests ranged from the veldt to the phone company — offers a solution.

Conservation International senior scientist Lee Hannah, Guy Midgley of the Kirstenbosch Research Center at the South African National Biodiversity Institute, and Steven Phillips and Aaron Archer, researchers at AT&T Labs, began with traditional conservation-planning software, which shows the location of current populations and possible future habitats.

They then integrated it with “network flow” software, which is used to optimize flows in a range of commercial applications. It helps telecommunications to optimize the efficiency and capacity of calling networks, and in the airline industry to determine how to link aircraft distribution, routes and schedules to get the most out of their fleets. Ground-based manufacturing, shipping and retail companies may also use network flow software to make decisions related to effective warehousing and distribution of products.

As the researchers wrote in a 2008 paper, their method “addresses both the biological needs of multiple species and the social and financial desirability of minimizing the amount of land requiring protection.”

“Species-conservation software provides a range of answers about where to establish corridors to capture the greatest number of species in the least amount of area,” says Hannah, who worked with Midgley to create the model that identifies where species are today and where they will be at 10-year intervals between now and mid-century. “But there is a single-best answer to that question, and in general, you arrive at it by using commercial optimization software.”

Phillips works at AT&T in telecommunications optimization, but has been interested in species conservation modeling for nearly a decade.

“My role was to observe that dispersal corridors can be modeled and optimized using the concept of network flow, which is widely used for modeling connectivity in other fields,” he says.

For the test case — the roughly three hundred species of protea plants found in the South African South Cape Floristic Region — the hybrid software’s solution not only connects existing populations with nearby future habitat, but also requires 30 percent less land than is suggested by traditional species-conservation software focusing on corridors.

The approach is made clear as the software runs on a laptop computer. With a species of protea selected and the software activated, the screen fills with a map of the region, overlaid by areas of color indicating where populations of the species are currently found. A time-lapse feature then shows the species’ likely migration path as climate changes.

As the screen animation continues, other areas of color appear, indicating locations of current protected areas. The optimizing algorithm then identifies sections of land close to a reserve that, if protected, would link a species’ current range to its future range while using much less land than corridors typically require.

“It doesn’t try to create a corridor; it adds area at the edge of existing parks,” Hannah explains. “We use species models and conservation-planning software to decide where to put new protected areas in response to climate change. We know that most of the preserves are not in the right places because they were established before climate change was considered. This approach lets us answer the question, ‘If you did design for climate change, where would you put the protected areas?’”

Policymakers today think about a range of actions they can take to protect species during climate change, such as creating gene banks, physically moving species, and creating corridors.

“There is a whole spectrum of feasible actions,” Hannah says. “In the past, people have seen links between protected areas as being big corridors between parks. But you don’t need that; you need to link existing populations with existing parks that can become strongholds for species in the future. If you’re addressing climate change, corridors are not the most efficient option for protecting species. Eventually, corridors will give way to this.”

Consider it part of the changing landscape of conservation strategy.