The Slow Recovery of a War-Torn Ecosystem
The swimming pool at Chitengo Camp is a bright blue circle shaded by trees. It is a tranquil place to relax after a dusty game drive in Gorongosa National Park, but not long ago this inviting oasis was used by rebel forces as a prison.
The pool, now ringed with deck chairs, instead of armed guards, is just one small sign of how far Mozambique’s prized park has come since a 15-year civil war broke out in 1977 and the country descended into chaos.
“The park was cleaned out,” explained Kathryn Grabowski ’16, a civil and environmental engineering student at Princeton University. “Armed forces swept through the park killing anything they could eat or sell.”
But now, more than twenty years after peace was restored, the rich array of wildlife, which earned the park its nickname: “the place where Noah left his ark,” is on the rebound.
It is that slow and complicated recovery process which brought Grabowski to the Park in the summer of 2015, funded by the Becky Colvin ’95 Memorial Award, to study an ecosystem on the rise. The award is presented annually by the Princeton Environmental Institute (PEI) and the Department of Ecology and Evolutionary Biology in support of field research projects critical to the senior thesis.
“Gorongosa provides a rare natural experiment for exploring the ecological consequences of major species loss on ecosystem functioning,” said Grabowski. “During the civil war, 90 to 100 percent of individuals of all species of large mammals were wiped out. Studying how the park responds to this loss is hugely relevant at a time when we are losing species at a rate comparable to the last major extinction event.”
“Katie is really doing some of the pioneering and groundbreaking initial research on these recovering wildlife populations in this war-torn ecosystem,” said Grabowski’s adviser Rob Pringle, assistant professor of ecology and evolutionary biology at Princeton. “There’s very little data about this park either before, during or after the war, so it’s all part of getting a foothold — a knowledge base in the ecosystem.”
While the park is recovering, it still looks very different than it did before the war. Back then, Gorongosa was home to over 10,000 buffalo, in addition to thousands of wildebeest, waterbuck and zebras. The park also boasted iconic predators like leopards, lions, wild dogs and spotted hyenas. Today, the only predator left is the lion and the population is just 25 percent of what it used to be. While most herbivores are returning, the balance of species is markedly different. Most notably, waterbuck, a large antelope with distinctive spiral horns, have rebounded well beyond their pre-war population size, even as other species are still struggling to return to their former numbers.
In addition to these dramatic changes, there has been a subtle shift underfoot. Before the civil war, grasses dominated the park’s floodplains. Today, plant groups known as forbs — a classification that includes clover — dominate these areas.
“Forbs are generally less palatable to herbivores than grasses,” explained Grabowski. “So this shift may mean that the plant communities of the floodplains are simply no longer able to support the wide array of herbivores they used to.”
The relationship between grazing and plant response is complex. Some species grow best when grazed, while others decline. Grabowski was curious if the loss of herbivores during the civil war could have actually triggered the switch from a grass to forbs dominated landscape, which might now be preventing the recovery of some grazing species.
“If grasses need to be grazed in order to outcompete forbs, then the loss of herbivores could have given forbs an advantage,” said Grabowski.
Armed with a pair of clippers and experimental plot markers, Grabowski embarked on a series of experiments designed to mimic grazing. She took on the role of herbivore and carefully clipped down the vegetation in her plots. Several weeks later the responses of the different species in each plot were assessed.
“If heavy grazing before the war kept the floodplain mostly grass, I would have expected to see the grass in my experimental plots benefit from clipping more than the forbs,” Grabowski explained. “My data didn’t show this. But there are many factors including my method of mimicking herbivory — very intense pulses of grazing — that might have influenced these results.”
During her short two months in Mozambique, Grabowski also conducted observations of waterbuck, the now dominant species on the floodplain, to try to better understand how this species spectacular recovery might be influencing the larger ecosystem and the recovery of other herbivore species.
“Waterbuck may be playing a role in preventing grasses from re-establishing dominance by preferentially feeding in grass-dominated areas,” said Grabowski. “But my data did not show this effect.”
Although Grabowski did not find clear answers to the research questions she set out to investigate, her research has laid an important foundation for future field work.
“Katie is an incredibly meticulous student and one of the most careful and thorough undergraduate researchers that I have ever had the pleasure of working with,” said Pringle. “It has been incredibly rewarding to watch her develop and see the increase in sophistication in how she thinks about these questions and approaches experimental biology field research.”
In addition to honing her research skills and learning how to work around all the unforeseen issues that arise when one’s lab is a field and one’s test subjects are antelope, Grabowski used her time in Mozambique to check quite a few things off her bucket list.
“I was lucky enough to see young lions wrestling in the grasses and to ride in a helicopter,” said Grabowski.
After graduation, armed with her degree, research experience and a certificate in environmental studies, Grabowski heads to Orlando, Florida to check one more thing off her bucket list – working at Disney. For the next year she will be a Conservation Education Presenter at Disney’s Animal Kingdom. It will be a big change from field research in Mozambique, but for Grabowski it is just one more opportunity to support conservation efforts around the world.
In addition to Kathryn Grabowski ’16, Connor Stonesifer, ’16, ecology and evolutionary biology major, was also awarded Colvin funds last spring. The Becky Colvin Memorial Award supports summer field research projects in support of the senior thesis. The award was established in 1995 by Dr. and Mrs. Robert Colvin in memory of their daughter, Becky Colvin ’95. Becky was an ecology and evolutionary biology major who was very interested in field research. Students are selected to receive the Colvin Prize by competitive application in the spring of their junior year.
Additional information about the Becky Colvin Memorial Award and prior recipients of the prize is available on PEI’s website.