At the population level

Population ecologists study how and why the numbers of individuals of a species change over time. In Gorongosa, their questions include: How many zebras, hippos, and elephants need to be reintroduced to ensure genetic diversity? Which populations are rebounding and which are not? Why?

Gorongosa National Park in Mozambique experienced a dramatic loss of large mammals during and after a civil war (1977–1992), with subsequent cascading effects on vegetation. Could the ecosystem recover? The government of Mozambique believed it could, and in 2008 entered into a $40 million, 20-year agreement with a U.S. nonprofit organization, the Gorongosa Restoration Project (now known as the Gorongosa Project). The goal was to restore and conserve the park’s biodiversity and to engage the surrounding communities in sustainable development. During this course, we have investigated ecological patterns and processes at different scales. Now, we return to Gorongosa and ask: Has the park’s ecosystem recovered? What does a successful recovery look like, anyway? Who defines success, and how do we measure it? How has the nature of the system changed? And what opportunities and challenges lie ahead?

In August 2006, 54 Cape buffalo were translocated from South Africa’s Kruger National Park to a designated “sanctuary,” a 6,200-hectare, fenced-off area within Gorongosa National Park. This was the first step in an expensive and complicated endeavor to rebuild the park’s populations of large grazers with individuals from Mozambique, South Africa, and Zimbabwe. Blue wildebeest (which, like Cape buffalo, had been reduced to extremely small populations in Gorongosa) and eland antelopes were next, as well as several hippos and elephants to increase the genetic diversity of the park’s remaining populations. Not all efforts succeeded (e.g., none of five translocated cheetahs survived), but by 2013, 186 Cape buffalo, 180 blue wildebeest, 35 eland antelopes, six bull elephants, and five hippos had been successfully added to the park (see Figure 1). An additional 14 Crawshay’s zebra, a distinct subspecies, were translocated from other areas in Mozambique to help rebuild the local herd, which had dwindled to fewer than 20 animals.

Figure 1. Cape buffalo and blue wildebeest. Cape buffalo and blue wildebeest were among the first species translocated to Gorongosa National Park to increase genetic diversity and rebuild herds of large grazers. Cape buffalo, ©Piotr Nasrecki/Gorongosa Project; wildebeest, © Scott Presnell/CC BY-NC-ND 2.0

By many measures, the park has experienced a remarkable recovery at the population level. In late 2014, an aerial count, the eighth survey of all large mammals in the park since the civil war, yielded encouraging numbers. Covering 183,200 hectares, or roughly 49.7% of the park, a helicopter crew counted a total of 71,086 herbivores of 19 species (see Table 1). Recall that in the year 2000, the combined total of all elephants, hippos, wildebeest, waterbuck, zebras, eland, buffalo, sable antelope, and hartebeest was less than 1,000 animals! With the exception of Crawshay’s zebra, populations of large grazers were now large enough for continued recovery and viability. A new survey in 2016 confirmed the trend (78,627 counted), despite very dry conditions during the intervening two years. Waterbuck have become so abundant that Gorongosa has contributed individuals to populations elsewhere in Mozambique.

Results from the 2014 and 2016 aerial wildlife counts

Table. 1. Large mammals were counted by helicopter in 2014 and 2016. These represent the absolute minimum number of large animals that occur in Gorongosa Park. Several species have increased substantially between the two surveys, including impala, nyala, and kudu. However, other, smaller species (e.g., oribi, reedbuck, warthog) saw a decline in numbers. These more selective feeders may have been more heavily impacted by the drought conditions of the intervening years. Data courtesy of Gorongosa Project

Figure 2. Waterbuck recovery from 2001 to 2014 Maps of Gorongosa National Park from 2001 (left) and 2014 (right) showing the expansion of waterbuck. (Red dots represent observed individuals.) ©Gorongosa Project

It is important to note, however, that current populations differ significantly from pre-civil war levels, in both numbers and proportion. Most herbivores are at 10%–50% of their historic population levels. Waterbuck are one exception: their abundance has increased tenfold, changing the ecosystem from one dominated by buffalo to one dominated by waterbuck (see Figure 2). The 2014 wildlife count revealed what is likely the single largest population of waterbuck found in any of Africa’s protected areas! This trend continued in 2016 despite drought conditions. In contrast, zebra populations have experienced the most dramatic decline, to fewer than 20 animals from a pre-civil war herd of ~3,500. The rapid recovery of some herbivores may reflect the continuing absence of large predators. Only an estimated 50–70 lions currently live in the park, which was once famous for them. Prides are smaller, making them more vulnerable to collapse if they lose a key member. Few, if any, leopards or hyenas remain. Scientists are trying to figure out why these predators haven’t rebounded yet given the increased abundance of prey.

At the community level

At the community level—where the focus is on the connections between groups of species and their effect on species diversity and relative abundance—ecologists in Gorongosa are asking questions like: How are plant species responding to the recovery of large grazers in the park? How will a system dominated by waterbuck affect the community structure? Or the absence of zebra herds? Researchers are studying the changes to Gorongosa’s ecological regimes and their effects, such as whether the large grazers are halting woodland expansion, and whether other functional roles these herbivores once carried out, like seed dispersal, are resuming.

From a recovery standpoint, Gorongosa has already achieved some success at the community level. Large grazers eat tall grasses, which has given smaller herbivores like impala, oribi, bushbuck, and reedbuck greater access to the short grass they prefer (see Figure 3). Consequently, those species appear to have rebounded on their own. On the other hand, in the absence of the large zebra and buffalo herds that historically dominated Gorongosa, the remaining lions (Figure 4) are targeting smaller prey, such as warthog, bushbuck, and reedbuck. Is prey composition affecting the recovery of Gorongosa’s lion prides? Park staff are also investigating other potential factors limiting lion recovery, including prey abundance, genetics, disease, and human impacts such as poaching.

The way communities respond to disturbances can reveal their complexities. The direct and indirect effects of one species on another change over time and depend on webs of relationships with cascading effects. As park populations continue—or fail—to rebound, questions for community ecologists will proliferate. Scientists will continue to monitor how Gorongosa’s populations change over time and the effects upon community compositions and the larger park ecosystem.

Figure 3. Reedbuck, oribi, and impala. Smaller herbivores like reedbuck, oribi, and impala (counterclockwise from top left) have rebounded on their own with the return of large grazers to the Park. ©Piotr Naskrecki/Gorongosa Project

At the ecosystem level

At the ecosystem level, ecologists study the interactions of organisms within a community and with their physical environment as an integrated system: an ecosystem. Ecosystem-level questions delve into these interactions and which sets of interactions could be targets for restoration. Should restoration efforts aim to recreate a historical baseline, or should they embrace a “new” Gorongosa ecosystem? How will we determine whether Gorongosa has recovered as an ecosystem? Ongoing ecosystem studies and monitoring will increase our understanding of how the pieces fit together and ultimately help answer these questions.

Figure 4. Lions. Large carnivores, like these lions, have yet to recover their former numbers in the park, despite a new abundance of prey. ©Brando Vandudzi

As a critical first step, park staff are working to establish a baseline for biodiversity in the park. Baseline ecosystem monitoring currently includes: annual biodiversity surveys; vegetation composition and structure monitoring; and wildlife population monitoring (e.g., the aerial survey mentioned earlier). They are also at work on a comprehensive inventory of all life in Gorongosa, described on the park’s website as “the first large-scale, all-taxa survey of a complex ecosystem in Africa.” Results to date (2017) include some 465 bird species (such as the green-headed oriole, endemic to East Africa); 152 mammal species (with more than 30 types of bats); 86 reptile species and 54 amphibian species; 51 species of fish; more than 1,800 insect species; at least 100 other species of invertebrates (mostly mollusks, as scientists have yet to sample other groups); and more than 1,880 plant species. On Mount Gorongosa, scientists identified an unnamed species of land crustacean, the only one of its kind ever found in the African continent (Figure 5). Several species of plants believed to be endemic to the Eastern Highlands of Zimbabwe have been also found on Mount Gorongosa, and in 2013 over 100 ant species, 33 frog species, and 47 reptile species were documented on the Cheringoma Plateau alone.

Figure 5. Gorongosa’s spiny crustacean. An unnamed species of land crustacean found on Mount Gorongosa, the only one of its kind ever found in the African continent. Similar species are found in Madagascar and a few Pacific islands. ©Piotr Naskrecki/ Gorongosa Project

Monitoring efforts in Gorongosa also describe abiotic factors and their effects on the ecosystem. Managers at Gorongosa National Park have defined several key research questions, such as: What maintains the Lake Urema floodplain system? How do changes in land use affect water quality? How will climate change affect the ecosystem? How are land clearing and deforestation affecting it? To find answers, park managers use a combination of monitoring techniques. For instance, satellite imagery and a local weather station help monitor the frequency, intensity, severity, and seasonality of fire in the park. Fire is considered to be exacerbated by climate change, human population growth, conflict, and a breakdown in traditional management practices. Scientists are also doing experimental work on the potential effects of drought on plant species widely distributed throughout the park for insight into how the ecosystem might be shaped by climate change (Figure 6).

Figure 6. The effects of climate change on trees in Gorongosa National Park. In addition to research on Gorongosa’s wildlife, scientists are studying the potential effects of climate change on the park, which is predicted to experience increased drought in the future. For example, Massad and Castigo (2016) investigated how the distribution and community composition of different tree species (like Faidherbia albida, pictured) may respond to drought. This knowledge will help predict future ecosystem functioning and inform park managers concerned with changes in resource availability. Roger Culos, Creative Commons

Monitoring these ongoing changes enables park scientists and managers to identify threats and to introduce appropriate and adaptive management actions to mitigate them. Scientists are hoping to track Gorongosa’s recovery, assess the effects of climate change, and learn about ecosystem functioning. Current management actions aim to mitigate human impacts rather than achieve any specific state. How closely the new Gorongosa will resemble its pre-civil war state remains to be seen.

People in the Gorongosa ecosystem

As the park’s website states: “… the health and security of the Gorongosa ecosystem is directly linked to the health and security of the people living around the Park.… Our goal is healthy families with improved food security, alternative, sustainable livelihoods, and reduced population pressure around Gorongosa.” To meet this goal, the Gorongosa Project and the park have several ongoing initiatives. Local scouts have been hired as tourist guides, and since 2009, 20% of tourism revenue has been allocated to the surrounding communities. Health services are a priority and to date have included launching mobile clinics, training community health workers, and distributing mosquito nets to everyone living in the park’s buffer zone (~250,000 people). Another priority is conservation education. A new community education center teaches children about the environment and farmers about sustainable agriculture (see Figure 7).

Challenges remain. Mozambique is one of the poorest countries in the world and Gorongosa lies in one of its poorer districts, which understandably makes it difficult for surrounding communities to prioritize conservation. When Mount Gorongosa was added to the park, local people lost access to traditional activities and resources. Illegal activities, such as poaching for bushmeat, continue—an indication that there is more to do in terms of fostering alternate livelihoods. For example, in the 2014 aerial count, two poachers were arrested with a Lichtenstein’s hartebeest, and other snared animals were spotted. Surveys have also documented commercial timber cutting and trees being cleared for farmland. At the government level, in 2013 a new conflict erupted between the ruling party, Mozambique Liberation Front (Frelimo), and the main opposition party, Mozambique Resistance Movement (Renamo), over charges of corruption. These tensions temporarily closed the park in 2014, because Renamo was using part of the Gorongosa district as a base. A permanent ceasefire was announced in mid-2017, but this hinges on several issues that will take time and may not be resolved quickly.

As noted, it can be difficult to balance the twin goals of conservation and development. Sustainable recovery efforts must recognize the role that people have played in shaping and maintaining the region. This again raises the question of what the target ecosystem state should be, as different stakeholders may disagree over what level of management is optimal or to what extent human impact should be mitigated.

In conclusion: evaluating success

In August 2017, the government of Mozambique renewed their agreement with the Gorongosa Project, stipulating an additional 25-year commitment and minimum additional funding of $30 million. As an ecologist, would you cite Gorongosa as a conservation success story? How about as an anthropologist? Or a local community member? As a government minister? How about as a systems thinker? How could a better understanding of ecology and the park’s ecosystem dynamics guide management and decision-making?

Figure 7. Conservation education. The Community Education Center (or CEC) was completed in 2010 and works with teachers, school groups, park employees, and local leaders in Gorongosa district. ©Gorongosa Project

This week we asked whether Gorongosa’s ecosystem has recovered. As we now know, the answer is complicated; these wicked problems are not easily solved. In Gorongosa, as elsewhere, threats to conservation are underlaid and exacerbated by social and political contexts and linked to other, evolving problems. Conservation approaches, like adaptive management, recognize that success is a moving target. Continuous monitoring of status and trends, and incremental, iterative interventions, can help us address components of the problem while learning more about how the whole system functions. New conservation ideas, like the biocultural approach, can improve local engagement and collaboration for long-term solutions. With this diversity of tools, which themselves continuously evolve in response to new knowledge from many sources, a recovery seems possible.

By Kimberley Landrigan, Suzanne Macey, and Ana Luz Porzecanski

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