Designing corridors: the big picture

We have contributed to over 30 linkage designs in California and Arizona. We failed at this task when we tried to tell managers what to do. We succeeded when we asked management agencies and conservation organizations how we could help them identify wildlife linkages at risk and develop plans to conserve them. We share four lessons.

  1. It is more exciting and rewarding to work for connectivity than against fragmentation.
  2. Be a team player on everything—and that means involving non-scientists in science!
  3. Linkages must be designed for multiple species.
  4. The linkage design plan must be comprehensive - it is not just about getting the animal across the road.

Lesson 1: It's better to work for connectivity than against fragmentation

I (Paul Beier) had barely heard of corridors when I started a 5-year study of mountain lions in southern California in 1988. But I soon learned that mountain lions were on the road to extinction in every southern California mountain range. As the encirclement of each mountain range became complete, each mountain lion population would wink out, one by one.

It is more exciting and rewarding to work for connectivity than against fragmentation.

But it doesn't have to end that way. In 1990, mountain lions were still moving between mountain ranges. If they could continue to do so, they could survive in every linked mountain range. More important, by radio-tagging cougar cubs, I learned that these animals would find and use narrow, highly disturbed corridors through urban areas. Imagine how successful a corridor would be if we designed them to facilitate movement by animals. Not just mountain lions, but also badgers, jackrabbits, bighorn sheep, arroyo toads, steelhead trout, and even plants and invertebrates at risk.

As recipient of these scientific insights, I felt obliged to bring them to the attention of managers. I published scientific papers on my findings, but I knew managers wouldn't read them. So for the next 7 years, I did the only thing I could think to do. I fought against proposed projects that would sever the two potential corridors linking the Santa Ana Mountains (my study area) to other areas. I read environmental impact reports and wrote scathing critiques of them. I testified at hearings on proposed projects. I wrote letters to the editor, and helped reporters write news stories. But mostly I fought proposed housing developments. Typically I'd end up with a few token mitigations that left the corridor worse off, but perhaps not as bad off as it could have been.

Your goal is not slowing down the rate at which things get worse; your goal is to make the landscape more permeable than it is now!

This work had to be done. I am glad I did it. But fighting development proposals is not a strategy for victory. A victory may stop one bad project, but next year there will be another proposal, just as bad, on the same piece of ground. It took me 7 years to figure out that we could only win if we moved beyond reacting to bad proposals and put forward a positive proposal—a linkage design.

Lesson 2: You don't lead by getting others to follow you

Having learned to work for connectivity, I worked on an effort that produced the “South Coast Regional Report”—basically a map of a connected wildland network in California. But the South Coast Regional Report had a fatal flaw: It was a plan written by 15 PhDs who wanted to help the befuddled management agencies see the need for connectivity. While I'm sure we did help some managers think about a positive vision for a connected wild system, many managers saw that our map failed to connect some important wildlands under their jurisdiction. If they had been part of the process, they might have agreed with our priorities, but instead they were handed a map and told to “make it happen.” Worse yet, most managers, already forced to read the mountain of paperwork from their own agency, didn't even have time to pick it up the Regional Report. The Report gathered dust. The press ignored it.

This time we learned faster. If you want agencies to read a document, it really helps if it is their document! And a year later, when 5 big agencies invited managers to a workshop to create a map identifying wildlife corridors at risk, 200 of them showed up and enthusiastically contributed to the Missing Linkages report. When we asked how we could help, they gladly said “Please take all our input and write up the report and put our logo on it.” Ironically, when we tried to lead (I'll write a report for you to follow) nobody followed, and when we served (How can I help all you agencies tackle this difficult problem?) we were given the very sort of power we had earlier wrongly assumed was our natural right as scientists!

Lead by serving. Leadership is not “getting others to follow.” Leadership is engaging diverse people to develop fair, sound, and comprehensive solutions to difficult problems.

When the report came out, managers read it. They had to—it bore their logo. And they liked it. Quite honestly, the report written by 200 people, mostly non-scientists, was better than the report by 15 PhDs. These 200 people knew more than we did about what was important. They loved the land as much as we did. They were just as passionate about creating a landscape more than the sum of its parts, because they owned the parts.

None of us is as smart as all of us. There are a lot of great people who will do great things when they work as part of a team rather than as gophers for scientists who fancy themselves as leaders.

This lesson has permeated every aspect of the linkage designs that are now being successfully implemented in southern California. The Missing Linkages report ( was a map of potential linkage areas at risk. The next step was to identify the top priorities for detailed plans and immediate action. Instead of relying solely on scientists to prioritize linkages, we invited every interested party to another workshop to select criteria. After participants saw the priorities resulting from the first weighting scheme, they argued to change the weights. It took forever, but at the end of the day, each participant agreed that the final criteria were better than the scheme each of us had advocated at the start of the day. And everybody owned the final priorities.

At virtually every juncture in the linkage design process, we had another workshop. As a scientist, I took a while to embrace the idea of inviting non-scientists to participate in scientific issues. But science is nothing more than a way of knowing that is transparent, evidence-based, logical, and open to correction. No assumption or logical chain in ecology is so esoteric that a manager can't understand it. A scientist who wants to be a conservationist simply must invite managers to participate in the science. The product is improved by having managers challenge our assumptions and offer alternative evidence and alternative interpretations of the evidence.

Who should be invited to participate? Land management agencies, state and federal wildlife management agencies, conservation NGO's, transportation agencies, county and municipal planners, local land trusts and conservancies, first nations (Native American tribes, etc.), military bases, utility districts, developers, ranchers, universities and other research entities, and biological consulting firms.

Lesson 3: Leave no species behind

Because large carnivores like bears and wolves live at low density and are among the first to be harmed by loss of connectivity, they are appropriate focal species for linkage design. And people love them, so they are popular flagships to increase public support for a linkage. In fact, large carnivores are the only focal species in about half of all published linkage designs based on focal species. But please don't design a linkage solely for large carnivores—or any single species! Many other species need linkages to maintain genetic diversity and population stability. Furthermore most large carnivores are habitat generalists that can move through marginal and degraded habitats, and a corridor designed for them does not serve most habitat specialists with limited mobility.

Develop linkage designs to accommodate all species that move between wildland blocks; not just large carnivores

Finally, implementation of a single-species corridor for large carnivores will have a “negative umbrella effect” for the other species. We simply cannot ask land use planners and conservation investors to create a mountain lion corridor this year, and then come back and ask them to add a bighorn sheep corridor next year, and a desert tortoise corridor the year after that. If the mountain lion is going to be an umbrella for biodiversity, it must be part of a linkage designed for a broad array of native species.

Lesson 4: A linkage design is not just about getting animals across the road

Conserving land will not create a functional linkage if major barriers are not mitigated, an excellent crossing structure will not create a functional linkage if the adjacent land is urbanized, and an integrated land acquisition-highway mitigation project could be jeopardized by inappropriate practices (e.g., predator control, fencing, artificial night lighting). An adequate linkage design will recommend crossing structures and management practices to restore native vegetation and minimize the impact of exotic species, fences, pets, livestock, and artificial night lighting. An emerging issue is how to mitigate the impact of fences, mowed strips, and stadium lighting designed to discourage human traffic on international borders.

The linkage design also must address how landowners living in or adjacent to the linkage area will become stewards of the linkage. Of course, in keeping with the philosophy that “None of us is as smart as all of us,” landowners will have been invited to participate from the outset, and some of them will already be on board. Many homeowners may initially decline the invitation to work on the plan. But once the plan is on the street, it may be necessary to ask all homeowners to help, either through individual voluntary actions, through a homeowners association, or in other ways.

A wildlife linkage is “all edge” and will require active management forever. The linkage design may ban off-road vehicles and eradicate major invasive plants, but in another decade there will be another recreational threat and a new invasive plant. Your plan cannot address all of these. But if it is to have any hope of being more than a pretty map, it must comprehensively address land conservation and roads and management practices and involve landowners as stewards.