The goal of conservation is the preservation of wilderness at risk and almost, as a rule, this is achieved by conserving certain places and certain species. This system has worked beautifully with populations that don’t move around much but has largely failed when it comes to protecting migrants. Put simply, migratory populations are those that move from one place to another and back again. When we fail to include these populations and their pathways in our conservation planning, we risk building a fatal flaw into our most well-laid conservation plans.
2016 marks the 100-year-anniversary of the National Park Service (NPS). Since its inception a century ago, the NPS has been on the forefront of American conservation. Thanks largely to its successes in setting aside spaces for the protection of wildlife, we haven’t continued to see the major die offs and extinctions that marked the early history of the United States. While the herds of bison that once famously roamed in the millions through the American midwest may be largely gone, healthy and stable populations exist on managed lands in twelve states. Nearly half of these are found in Yellowstone National Park. The visibility and viability of our National Park System coupled with their well-documented successes have helped to create the current conservation culture and the methods it employs. Most of the time, the culture focuses its efforts on setting aside habitat and protecting animals where they live.
In 2001, the NPS published a report titled “Rethinking the National Parks for the 21st Century”. In it they outlined both the strengths and weaknesses of the park system as it exists and noted the following:
“Actions to preserve biodiversity cannot be limited to park areas, for parks are often parts of larger ecosystems that encompass them. To encourage ecological stewardship outside the parks, the Service should cooperate extensively with its neighbors—federal agencies, states, counties, cities, tribes, the private sector, even other countries. Parks cannot survive as islands of biodiversity. They need to be linked with other natural areas through wildlife migratory corridors and greenways.”
This report makes explicit the realization that changes in major migrations are likely to have major impacts on the ecosystems they pass through as well, including those that are otherwise protected.
Wildebeest are famous migratory species and one which we are lucky enough to have here at Safari West. Every year, a massive herd of grazers (including zebra, Thomson’s gazelles, and a million or so wildebeest) roam up and down the Serengeti; taking part in one of the largest land migrations on the planet. As these massive herds travel they provide sustenance for innumerable predators. Lion prides with established territories take full advantage of this moveable feast as it winds through their territories. Giant crocodiles in the Mara River wait patiently for the feeding frenzy that occurs with the arrival of the herds. Should a highway project or urban development interrupt this migration, stopping all those ungulates in their tracks, it would trigger an ecological disaster. The huge numbers of herbivores would quickly overgraze the territory they had stopped in, damaging the environment and leading to starvation. Ahead of the broken migration, the predators would suffer. They’d begin to apply increased pressure on other prey species within the ecosystem and in all likelihood, populations would decline on both sides.
Wildebeest contribute to the ecosystem in other ways as well. Millions of wildebeest produce millions of pounds of manure and spread it far and wide as they travel. Not only does the savanna gain free fertilizer, it is also tilled by the motion of millions of sharp hooves. This constant cropping and fertilizing benefits the plant life of the Serengeti immensely. The Serengeti without this valuable soil amending service would be a much different place.
In North America, we’ve seen ecosystems shift as a result of failed migration already. Consider one of our most famous wild spectacles, the annual salmon run. Most Pacific and Atlantic salmon species have a life cycle that is highly dependent on migration. Born in tributaries and streams far from the ocean, young salmon move downstream to the sea where they mature. After several years and as they approach the end of their life cycle, the salmon return to the river mouths and commence a long upstream swim to their birthplaces. In some cases, this migration takes them from the Pacific coast inland as far as Idaho (a 900-mile swim against strong currents and rapids). Once they reach their natal streams, they breed and shortly thereafter, they die.
Salmon are very important animals economically and so benefit from regulations designed to prevent overfishing and keep the population strong. We’ve also become quite adept at supplementing wild born fish with fish from commercial hatcheries. As a result of these practices and others, salmon are under no immediate threat of extinction. This healthy population-count hides the fact that wild salmon populations have undergone a steep and steady decline over the last two centuries. Why? Because we failed to take migration into account. We’ve done a decent job limiting fishing and ensuring that there is always suitable breeding stock moving upstream, but we haven’t always been as good at protecting that freshwater pathway or the streams they start and end their lives in.
Salmon populations have been decimated by a number of anthropogenic causes, among the most famous of which are our dams. Dams have the two-fold impact of blocking mature salmon from swimming upstream while simultaneously directing downstream moving youngsters into power-generating turbines. We’ve made numerous strides to correct these problems, largely by adding “fish ladders” that adult salmon jump up to bypass dams and opening spillways for the youngsters to keep them from going through the turbines. All told, while the situation is improving a bit these days, salmon runs are barely a fraction of what they once were.
Still, the total population remains strong, and we can raise new salmon in commercial hatcheries, or even farm them outright if it comes down to it (environmentally disastrous but entirely possible), so does it matter if they no longer migrate upstream? The answer to this is a simple and straightforward, yes. The salmon migration is essentially a giant nutrient transfer system leading from the bountiful sea up into mountainous forests. As mature and heavy-bodied fish leave the ocean and swim upstream, one of two things usually happens. Either the fish die en route; perhaps caught by a bear or killed by disease, or they survive their marathon swim, make it to their spawning grounds, breed, and then die. Those that get eaten add their sea-sourced nutrients to the ecosystem directly. Those that die in other ways, decompose and fertilize the downstream habitat with nitrogen, phosphorus, and other nutrients. The salmon run is not only a critical piece of the salmon life cycle, it’s also an important source of nutrition that has major impacts on the river and forest ecosystem at large.
It’s interesting to note that while the loss of a migration results in a dynamically changed environment, migration itself is an evolutionary response to a dynamically changing environment. In a land of eternal spring, birds would have no need to fly south. If winter snows didn’t bury mountaintop vegetation, elk wouldn’t need to head to the valleys. If the Serengeti weren’t seasonally dry, wildebeest wouldn’t have to follow the rains. These things do happen, however, and life has found ways to adapt to the changes. In a dynamic world, movement is a key survival strategy. If the wildebeest stop migrating, their ecosystem will be fundamentally changed. If the ecosystem itself changes, however, if the dry seasons get longer, or the weather patterns move north, the wildebeest need to be able to move with them. The major problem with not considering migration when we think about conservation is that we often wind up boxing in our species at risk. If they cannot change with a changing world, they die.
Like the world at large, conservation has to be dynamic. We’ve conserved a lot through the careful creation and management of parks and preserves, but now we know that’s not enough. Now that we’ve learned that these parks cannot exist as islands cut off from the world, we’re adjusting our techniques. We’ve only just begun to step back and examine the systems that connect one protected patch of green to another but as we learn, we must incorporate that knowledge into our plans. The future of conservation lies not in slicing out plots of wild, but in learning how to protect the systems by which life continues to adapt to an ever-changing world.