A jaguar photographed in Braulio Carrillo National Park, Costa Rica, by a Tropical Ecology Assessment and Monitoring (TEAM) Network camera trap/Courtesy of the TEAM Network
Editor's note: The latest article in an occasional series on how national parks might serve as an impediment to the sixth mass extinction.
There are places in nature where the loss of a species or two won’t send shudders through the ecosystem or even cripple it. In the tropics of Central America, for instance, new research shows that having robust diversity among mammalian species will allow for the loss of a good handful or two of species without upsetting an ecosystem.
Dan Gorczynski, a Ph.D. student in Rice University's Department of Biosciences, made that conclusion after searching through more than 4,000 photos to see if human pressures on Costa Rica’s Braulio Carrillo National Park were leading to detrimental impacts.
The 108,970-acre Braulio Carrillo is facing outside development pressures. Located between San José, the country’s capital, and Puerto Limón, those pressures have left more than half of the lands that surround the park without forest, and yet that didn’t seem to have a negative impact on the park’s mammalian kingdom.
"It is a bit of a surprise," said Gorczynski in a university release. "Previous studies in other places have shown that trait diversity is more sensitive to human disturbance than species diversity. Trait diversity can decline more quickly than species diversity, both in cases where species go extinct and where they don't."
In layman’s terms, trait diversity can be viewed as the biological functions a species brings to an ecosystem. A wolf, for example, is a predator that can keep prey populations from booming out of control. A grizzly bear or a mountain lion can bring that same trait diversity to an ecosystem.
An agouti photographed in Braulio Carrillo National Park, Costa Rica, by a Tropical Ecology Assessment and Monitoring (TEAM) Network camera trap/Courtesy of the TEAM Network
Rice University Professor Lydia Beaudrot, who worked with Gorczynski on the project, said the research he did “quantified … a concept called ‘functional redundancy.’”
“So even though individual species are unique, you may have a number of species that have the same kinds of functions, the same kinds of attributes,” she explained during a phone call. “And in terms of thinking about maintaining the function and the health of the ecosystem, theoretically, even if you lose a particular species, if there’s another species than can perform the same functions, there may not be as much detriment to the health of the ecosystem.”
A lack of that redundancy can be seen at Isle Royale National Park in the United States. Just one predator at the park – wolves – can check the resident moose population. When the wolf numbers dwindled to just two because of inbreeding and the lack of ice bridges that could link the island in Lake Superior to the mainland and possibly allow wolves to provide Isle Royale’s wolves with a genetic boost, the National Park Service stepped in to transplant wolves onto the island rather than watch the moose population decimate the island’s forests.
For his research in Costa Rica, Gorczynski analyzed more than 4,200 photographs taken by camera traps between 2007 and 2014 to see if he could discern any weaknesses in species that could be linked to a weakness in the park’s functional redundancy due to outside development. He looked at the mammalian ranks in Braulio Carrillo and “quantified, based on the traits that he was looking at, how many species could you lose before you start seeing a decline in the functional diversity” of the ecosystem, Beaudrot explained during a phone call.
“Based on the way he quantified it, you could lose up to nine of the mammal species -- he’s looking at 21 mammal species totally -- and maintain the same level of functional diversity. … That suggests that even with the loss of a number of species you could still have the same ecosystem functions and ecosystem health, which suggests some level of resiliency to species loss.”
In the end, Gorczynski saw no weaknesses, and there were no loss of mammalian species during the study period.
That redundancy at Braulio Carrillo supports robust trait diversity perhaps isn’t so surprising. With 135 mammalian species, the park that claims both cloud forests near its roof that tops out at nearly 10,000 feet and lowland rainforests showcased its resiliency to the researcher.
U.S. national parks rarely can claim such redundancy. The loss of apex predators such as the wolf has led to Park Service culling of elk in Rocky Mountain and other national parks, and even bison at Grand Canyon National Park; the same is done to check deer numbers in Eastern parks.
While nature has built-in resiliency to a certain degree, said Beaudrot, the bottom line for that resiliency is how much humans impact an ecosystem.
“Typically, I would say our parks here in the United States, they’re certainly better protected than a lot of tropical protected areas, tropical national parks, because there’s more resources available,” the professor said. “So there’s more active management going on here in the parks in the U.S. than in a lot of the tropics.”
And national parks in tropical regions often encounter greater human pressures, she said.
“Based on what we generally know about ecological theory, one might hypothesize that, potentially, tropical systems could be more resilient because they are thought to have higher redundancy,” Beaudrot said. “They have more species and they may have more species that fill similar roles. At the same time, though, human population growth is highest in the tropics, and a lot of the natural resource-based economies in tropical countries lead to over-extraction and over-use and illegal, rampant hunting.
“Illegal hunting is a huge issue, and of course extraction for deforestation for use for building materials and firewood for cooking. And illegal wildlife markets.”
Understanding that natural resiliency, and how human society can supplement it if necessary, could go a long way in maintaining national parks and other protected areas as impediments to the sixth mass extinction.
“I’d say, overall, national parks and protected areas more generally are one of our best tools for slowing extinctions and for maintaining wildlife because they provide the critically needed habitat.,” said Beaudrot. “Now, whether or not we have enough of them is a different question.
“E.O. Wilson has put a call out, it’s the ‘half earth strategy,’ or the half earth suggestion, that we really need to protect half the planet in order to be able to stave off these extinctions,” she said. “So I think yes, they’re critical, they’re necessary, but whether they’re sufficient, they’re probably not sufficient in their current state.”
Unfortunately for the U.S. National Park System, the toll from the loss of species has been significant. Three decades ago, researchers noted that parks such as Yosemite and Mount Rainier lost a quarter or more of the species originally found there. Smaller park units might have lost as much as 40 percent of their original species.
Still, lands managed by the National Park Service are biological outposts that can help prevent the loss of plants and animals to anthropogenic extinction. From Everglades to Great Smoky Mountains, Grand Canyon to Yellowstone, and Joshua Tree to North Cascades, these and their sister parks offer habitat, and in some cases refugia, for species being squeezed out of place by human actions responsible for habitat loss, pollution, and introduction of invasive species.
The challenge is not only to preserve those floral and faunal ecosystems as best as possible, but also to expand protected lands near them as well as near or around other parks that aren’t currently as ecologically robust as they could be and which could be isolated biologically.
“If you have an ‘island population’ and a disease comes through and wipes it out, then you don’t have any input individuals coming in if they can’t get there to help maintain what’s there,” said Beaudrot. “We know that movement between populations is incredibly important for long-term maintenance.”
Proof of that last point can be seen in the Yellowstone-to-Yukon effort to establish a protect corridor along which genes could transit, as well as efforts by the Wildlands Network to establish north-south corridors in the Northeast and through the western half of the United States and Canada.
How successful they ultimately can be remains to be seen.
Previous articles in this series:
Essay | National Parks As An Impediment To The Sixth Mass Extinction
Essay | What's Gone From The Parks?
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Comments
I truly regret being the party pooper. This truly is a good article that raises some thoughtful ideas. But, there's a lot to unpack here and the devil is in the details ...and in how they're presented and interpreted. Yes, in order to sustain and grow budding careers, researchers need to pursue and develop new ideas or at least promote new or expanded perspectives on ideas that might have been intuitive, but insufficiently illuminated in the past. And, I believe the work of Beaudrot and Gorczynski, mentioned in this article, makes a worthwhile contribution on some levels. However, I am worried these ideas, stated the way they have been here, could be used, by the usual suspects, to try to take public discourse in exactly the wrong direction. My worries are intensified by the fact that, as it is stated here, this work can be immediately misused to deflect, camouflage, and to attempt to falsely ameliorate concerns over detrimental human development and deforestation surrounding a national park.
Yes, we already know that "having robust diversity" among species will allow some loss of species without noticeably upsetting an ecosystem. We already know and have known that, in a healthy ecosystem, species occupy and utilize multiple overlapping ecological niches and multiple other species overlap in their occupation and utilization of those same niches, both horizontally and vertically, both up and across, ecosystem networks. Yes, you can call this phenomenon "functional redundancy" if you need to give it a handle, so far, so good. But, to then just generally assert that "the loss of a good handful or two of species" can be sustained without "upsetting an ecosystem" and to base this assertion on reviewing "more than 4,200 photographs taken by camera traps" spanning seven years is dangerously overreaching the limits of good science and, frankly, blurring the proper conduct of responsible conservation biology. I wish I could sugarcoat the problem here; but, I honestly can't.
Yes, I know the article specifically mentions that the deforestation that has "left more than half of the lands that surround the park without forest... didn’t seem to have a negative impact on the park’s mammalian kingdom" and that's certainly the conclusion that uninformed readers will take away. However, that conclusion ignores a host of crucial qualifiers.
First, Beaudrot and Gorczynski both seem to talk about "maintaining the function and the health of the ecosystem" and what is or is not a "detriment to the health of the ecosystem" and they seem to presume that they are using responsible definitions of an ecosystem, its functions, its health, and what does or does not constitute a detriment to any of that; but, they're really not. To voice what I know many botanists, mycologists, ornithologists, and entomologists might be thinking, an ecosystem consists of far more than its mammalian component, especially where they were working. But, their study and conclusions seem to ignore connections between human development and deforestation surrounding this national park, as well as its effects, detrimental or otherwise, on anything other than that mammalian component, which leaves multiple levels of misleading impressions.
Second, Beaudrot and Gorczynski both seem to presume that they can ascertain the health of even the mammalian component of that ecosystem by simply reviewing trail camera photographs only spanning "between 2007 and 2014" and only roughly seven years. Beaudrot also asserted that, to "discern any weaknesses in species that could be linked to a weakness in the park’s functional redundancy due to outside development," Gorczynski had "quantified, based on the traits that he was looking at, how many species could you lose before you start seeing a decline in the functional diversity" of the ecosystem. Gorczynski seems to think the ecosystem could "lose up to nine" of the twenty-one, almost half, of the mammal species he was monitoring and "still have the same ecosystem functions and ecosystem health." Again, I don't know how this team defines ecosystems or ecosystem health; but, their university is apparently paying them and funding them to be conservation biologists.
The article isn't clear on whether Gorczynski "quantified" the size of the various species' populations or just the number of different species seen in the photographs. This is an important question since trail photographs are not really optimal for estimating population sizes in individual species and population sizes in individual species are important because human development and deforestation change habitat, reducing it for some species and expanding it for others. Cockroaches generally don't mind; but, for other species, constraining their habitat will usually gradually constrain their population and constraining their population gradually constrains their vitality, which gradually constrains their ability to respond to stochastic events, and ultimately constrains their gene pool. By and large, it can be difficult to rigorously assess or even reliably notice these effects in trail photographs of mammals, especially larger mammals that have a longer reproductive lifespan, taken over a seven year timeframe. That's one or perhaps two generations for a jaguar.
The history of wolves in Yellowstone also raises questions about whether Gorczynski "quantified" the size of species' populations or just the number of different species as well as about Beaudrot's and Gorczynski's bold conclusions. Given the original presence of wolves, bears, and mountain lions in the park, Yellowstone originally should have been an example of the kind of "functional redundancy" that Beaudrot and Gorczynski now promote. However, during the period from the late 1930s through the early 1950s, Yellowstone should have still had sufficient bears and mountain lions to at least somewhat compensate for the extirpation of the wolves; yet, even then, the ecosystem was exhibiting clear problems. Although Yellowstone still had enough bears and mountain lions to be visually observed, their numbers had been, again, gradually constrained to the point where, by the early 1960s, the ecosystem was spinning out of control and, by the 1980s, it was already clear that this concept of "functional redundancy" had fundamental limits. The same could be said of Yellowstone's beavers.
Yes, the story of Isle Royale's wolves and how that small island had only one species of predator able to hunt the resident moose population demonstrates how it's better to have "functional redundancy" within an ecosystem. However, it seems to also be an example of how long it takes for gradual gene pool erosion to show up and, then, how quickly the effects of gene pool erosion can bring a species or even an ecosystem down. Seven years of trail photographs might get a dissertation done; but, they really won't reliably show the gradual impact of habitat loss and gene pool erosion. The stories of the mountain lions in Florida and, more recently, in the Santa Monica Mountains are also worth reviewing in this respect.
"In the end, Gorczynski saw no weaknesses, and there were no loss of mammalian species during the study period." Really? No loss of any specific mammalian species in a hundred thousand acre national park during the seven year period he studied? How many full extirpations was he really expecting under those conditions and in that amount of time? How many would he have had to personally witness in order for him to suspect the potential for an extirpation event of some kind? This is not a joke; this truly appears to be poorly and incompletely conceived science.
Third, given the current issues within conservation biology and public lands protection, I am especially worried that the flawed science and the seeming rush to overreaching conclusions in Beaudrot's and Gorczynski's work will end up amounting to misinformation, misinformation destined to be used as disinformation. We are already fighting battles over the need for endangered species protection. Will Beaudrot's and Gorczynski's flawed work be used to support efforts to replace species protection with some trumped up substitution of "functional redundancy" in ecosystems? We are already fighting battles over the need for critical habitat designations. Will Beaudrot's and Gorczynski's flawed work end up being used to undermine those arguments? We are already fighting battles over the detrimental impacts of human development, deforestation, mining, and other extractive and exploitive activities along the boundaries of our own national parks. Will Beaudrot's and Gorczynski's flawed work provide excuses to allow those activities? We are already fighting for more, better connected, and better protected public lands. Will Beaudrot's and Gorczynski's flawed work help or hinder those efforts?
And, Beaudrot apparently knows better or at least how to talk the talk. "I’d say, overall, national parks and protected areas more generally are one of our best tools for slowing extinctions and for maintaining wildlife because they provide the critically needed habitat... whether or not we have enough of them is a different question." "...we really need to protect half the planet in order to be able to stave off these extinctions." "If you have an 'island population' and a disease comes through and wipes it out, then you don’t have any input individuals coming in if they can’t get there to help maintain what’s there." "We know that movement between populations is incredibly important for long-term maintenance." Beaudrot knows these things; either her research or how her research has been reported doesn't reflect that knowledge.