Compared to the pre-war baseline, our results show an overall numerical population depletion of 77% across all mammal species during the war period, with some species experiencing a decline of up to 80% of their pre-war baseline abundance. Moreover, this degree of wildlife decline was not reversed by the end of the post-war period. This overall pattern of marked large mammal declines has not been previously documented at sites exposed to intense armed conflicts, which in Angola and other combatant countries profoundly dismantle the socio-political structure, natural resource management activities and enforcement practices such as bushmeat market inspection22,23. We emphasize that even during post-war peace times, wild mammal populations in Angola will fail to recover as long as rural people living in war-torn countries remain armed and wildlife management regulations cannot be enforced.
In Angola, there has been a process of slow disarmament of citizens by the government, which has disrupted hunting practices and reduced hunting pressure on local wildlife populations. However, meaningful recovery of institutional policy on protected areas and wildlife populations have not yet been implemented in all the Quiçama region, which is now largely occupied by a mix of native peoples, war refugees, and former combatants. As a consequence, post-war mammal population rebounds have been entirely restricted to some small-bodied species, likely due to their higher fecundity, in contrast with the low reproductive rate of medium- to large-bodied species, which continue to be slaughtered by fire weapons and other hunting techniques. Automatic rifle confiscation from citizens is an important factor in reducing hunting pressure, thereby favouring the recovery of local game biomass13,24. However, without the critical intervention of well-designed government policies, the baseline structure of large terrestrial vertebrate assemblages is unlikely to recover. For example, in the post war-zone Gorongosa National Park, Mozambique, the total biomass density of nine focal large mammal species had recovered in 2018 by ~ 80% of the pre-war baseline density, but the community composition had shifted dramatically compared to the pre-war baseline due to asymmetric recovery rates across species, with smaller antelope species exceeding the abundance of formerly dominant megaherbivores25. In particular, waterbuck abundance had increased by an order of magnitude, with more than 55,000 individuals accounting for over 74% of large-herbivore biomass by 2018. By contrast, elephant, hippo, and buffalo, which accounted for 89% of the pre-war biomass, now comprised only 23%25.
Considering carnivores, only lion populations in Mozambique’s Gorongosa National Park persisted throughout the war26, whereas leopards also persisted at intermediate abundance in forest environments in our study area. Both of these studies also recorded hyenas and jackals. At Quiçama, however, only two local informants had seen or killed hyenas or jackals over the last 5 years. The collapse of these carnivores has important ecological implications on their roles in key ecosystem linkages, such as necromass scavengers and energy and nutrient transfer27.
Defaunation can have important impacts not only in terms of severe depletion of vulnerable species but also on general ecosystem functions, including predation, herbivory, carrion removal and disease control28,29. For example, the Mozambican Civil War (1977–1992) induced to a catastrophic large‐herbivore die-off in Gorongosa National Park, which was followed by 35 years of woodland expansion, most severely in areas where pre‐war herbivore biomass was greatest7. This expansion included the invasive Mimosa pigra shrub—considered one of the world’s 100 worst invasive plant species30. Tree cover increased in four of the park’s five major habitat zones by 51% to 134%. Local informants in our study explained that in many areas of Quiçama the landscape have become more wooded since the collapsed of large herbivores, although this remains anecdotal. The most parsimonious explanation in both Mozambique and Quiçama is that a severe reduction in browsing pressure enhanced tree growth, survival and/or recruitment7.
Before the Angolan civil war, the protected areas of the Quiçama region once safeguarded one of the largest world populations of Red Buffalos (around 8,000 individuals) across both savannah and forest landscapes31. However, we found that poaching had severely reduced Red Buffalos to small populations restricted to some forest fragments in the southern Quiçama area. Landscape structure and vegetation cover clearly interfere with the degree of hunting efficiency because they affect hunter velocity, understorey visibility, size-selective prey detectability, and hunting techniques. In open savannah areas, larger animals can be easily detected, resulting in far more efficient use of long-range projectiles fired by automatic rifles and other weapons carried by distant hunters17. Also, compared to forest environments, motor vehicles gain much more feasible access into savannah landscapes when both pursuing prey and transporting carcasses to markets, which further explains the higher depletion rates of the savannah megafauna32. Mammals inhabiting more accessible open areas are therefore more vulnerable. For example, a study on Europe’s largest terrestrial mammal (Bison bonasus) showed that stronger pre-historic hunting pressure in open landscapes forced these animals into closed-canopy forest as a refuge habitat since the Pleistocene, leaving the legacy of the last native bison populations being restricted to forest areas15. However, habitat quality in forest refugia is not necessarily suitable. For instance, eland and roan antelope at Quiçama were unable to seek refugia in forest remnants, unlike other large-bodied species such as elephant and red buffalo. This likely explains why over 90% of our interviewees reported the conspicuous absence of those two ungulate species in the entire area.
Our model shows that commercially valuable target species in both savannah and forest habitats were not necessarily the most abundant during the early stages of the war. This is likely because the abundance of large-bodied species was then not low enough to discourage hunters from pursuing them. However, during the late and post-war periods, depletion rates of large-bodied prey in savannahs habitats were so high that pursuing them had become less worthwhile than pursuing midsized species. Because of the elevated time/energy costs of capturing large-bodied prey species in savannah areas, hunters become more selective in this habitat compared to the forest. On the other hand, given that levels of depletion of large-bodied species in forest areas were lower, most of these species continued to be killed in this habitat type, but resulted in smaller offtakes. Hunters also selected midsized species to compensate for any losses in the overall biomass of prey profiles. In the aftermath of the war, the gradual shift in prey size structure towards smaller-bodied species progressed and midsized species were most frequently selected by hunters in both savannah and forest habitats. In a study in Ghana, commercial trophy hunting for ivory, as opposed to subsistence hunting, was more sensitive to the density of elephants and enforcement efforts to inhibit poaching, supporting the notion that commercial hunting often depends mainly on overall prey abundance33.
Hunter preference for large- and medium-bodied species is higher because they yield higher catch-per-unit-effort in terms of meat biomass and other products (e.g. ivory and skin). As such, most species smaller than 12 kg were not a target game species and their relative abundance remained unchanged over the assessed periods. The fact of whether or not any given species had been reported as a hunting target during the war did not affect its pre- to post-war change in perceived abundance (see Fig. 4A) was influenced by the depletion of some small-bodied species which were not commercially harvested during the war, but were still hunted—because they were crop-raiders or depredated livestock—at a time when plenty of ammunition was readily available. That subsistence and/or commercial game hunting can have a profound detrimental effect on the biomass of large-bodied species has been widely documented34,35. However, we note that the abundance of medium-sized species at Quiçama continues to decline. In contemporary Africa, mammal populations have shown a ‘U-shaped’ abundance trend. Perhaps because small-bodied species are higher-fecundity and/or bypassed by hunters, large-bodied species have been targeted by wildlife management and conservation programs, whereas intermediate-sized species have experienced the steepest declines as they are usually hunted, but lack active management and can exhibit slow reproductive rates36. Therefore, there is a need to also directly manage midsized species, rather than assume that management actions targeting the most iconic ‘umbrella’ taxa will lead to effective conservation of all species. In our study area, for example, the greatest conservation focus should be allocated to bushbuck (Tragelaphus scriptus), currently the most hunted species at Quiçama (mainly for trade). This ungulate species has received no attention from regional to national scale conservation programs37.
We found little or no change in the relative abundance of small mammals, perhaps because these small-bodied species were neither commercially valuable nor harvested for local subsistence. However, comparing our results with other studies using combined sampling techniques such as camera traps, net, and microphones16, we recognize that some small mammals could have been undersampled, despite the enormous usefulness of LEK approaches in meeting the aims of this study. Regarding the primates, cultural influences such as food taboos may have important roles in mediating population declines of overexploited species. However, primates elsewhere in Africa and the Neotropics comprise the largest number of species threatened by hunting across the world’s mammals38. We therefore caution that the future bushmeat trade in Angola could, in fact, begin to target primates as other more desirable large-bodied species become gradually depleted and economically extinct. In addition, we highlight the increased risk of zoonotic diseases, given that our close phylogenetic relationship with nonhuman primates increases the likelihood of animal-to-human pathogen spillover39 and because the risk of disease emergence among mammalian orders is highest in bats (risk rate = 2.64), followed by primates (2.23), ungulates (2.09), rodents (1.81) and carnivores (1.39)40.
Modern armed conflicts affect terrestrial wildlife through a range of interactions, including tactical military operations. However, the consequences of socio-economic upheaval and livelihood disruption associated with a civil war can outweigh the direct effects of military activity9. Among the 24 mechanisms through which armed conflicts are known to affect wildlife, eight (86% of all existing case studies by 2016) were “non-tactical” pathways involving institutional decay, displacement of people and economic upheaval13. Accordingly, our results show that the main consequences of the war in the Quiçama region were non-tactical, such as much greater access to powerful fire-weapons, which were widely used by hunters and the military, even though their initial distribution purpose was to arm the population to fight against rival militias. The widespread use of automatic weapons intensified the overkill of large mammals, increasing hunting efficiency and the number of hunted species. In addition, wildlife culls were intensified during all brief periods of cease-fire because once the probability of encountering guerrilla groups was reduced, armed hunters felt safer and increased the amount of time allocated to hunting activities as well as the size of their catchment areas.
Ivory tusks from elephants killed at Quiçama were removed by the natural resource sector of each political party responsible for the catch, probably in exchange for automatic weapons1,41. Consequently, Angola’s elephants during the 1980s drew international alarm with reports of up to 100,000 elephants exterminated within rebel-controlled territories42. Park rangers were also victims of the threat from rebel groups, which was exacerbated by hundreds of outside hunters gaining access to the Quiçama area. Similarly, in the Okapi Reserve in the Democratic Republic of Congo, park guards were forced to abandon their posts following guerrilla attacks and were unable to prevent elephant poaching and bushmeat extraction13,43.
Strategic installation of both fixed and mobile military bases throughout protected areas is a tactical manoeuvre that greatly facilitates access to rifles and ammunition by all residents. However, in some situations this can potentially benefit wildlife populations elsewhere by effectively creating a “no human’s land”. This was the case in the Demilitarized Zone separating North and South Korea, which has been uninhabited by humans, thereby becoming a unique nature reserve containing the last refugia of Korean natural heritage23. Therefore, some pathways can show both positive and negative consequences for wildlife, depending on the spatial extent and timescale considered. In fact, if on one hand, exclusion zones often create protected areas for wild nature, on the other hand, sites overrun by war refugees will succumb to much greater hunting pressure. Where the civil war was most intensive in Eastern Angola, many populations of endangered wild species have been identified44, whereas in Western Angola, where the armed conflict was patchy or episodic, we found that wild populations of a similar set of species spiralled down into steep declines or were driven to local extinction. Despite intensive post-war efforts in clearing and deactivating landmines, millions of hectares of these explosive weapons zones remain under interdiction in Europe, Africa, and Asia45. This unpredictable distribution of landmines is also a double-edged sword because many refugees did not return to their original households after the war terminated because of risks associated with landmines. Some of the most intact ecosystems of Central America, for example, have not been threatened by habitat conversion by agrarian peasants because they were seeded with landmines during the civil wars46. Nevertheless, landmines also pose threats to wildlife, killing for example at least 30 elephants in Angola’s southern provinces42. Also, when landmines explode, they shatter soil systems, rip up plant life and disrupt water flows, all of which accelerate widespread ecosystem disruption46.
The main impacts of the Angolan civil war on terrestrial mammals of Quiçama occurred indirectly from military tactics or from “non-tactical” pathways and resulted from wholesale institutional and socioeconomic changes, rather than directly from military tactics. In view of all our findings and related literature, we present a summary flow diagram showing how modern armed conflicts can impact wildlife in modern war zones (Fig. 6). We divide the impact of wars into (A) tactical pathways, which are directly or indirectly derived from military unrest, associated military tactics or supporting military activities; and (B) “non-tactical” pathways, which stem from broad socio-political and economic changes associated with armed conflicts, including major institutional or policy failure, movement of refugees, and severely altered economies, local livelihoods and ecosystems.
Pathways through which modern armed conflicts can affect wildlife populations within war zones. Distinct pathways linking armed conflict to wildlife outcomes organized thematically in “tactical” pathways (which arise directly from the conflict itself and are associated with military tactics or supporting military activities) and “non- tactical” pathways (which stem from broad socio-political and economic changes associated with the armed conflict, including changing institutional dynamics, movement of people, and altered economies and livelihoods). Blue and red boxes represent either positive or negative effects, respectively.
Finally, we highlight that 36 countries worldwide are currently experiencing civil wars and most of these conflicts are fuelled or funded by international interests or started after an external intervention. These internationalized conflicts are more prolonged and less likely to find a political solution47. Mirroring our study area, protected areas confronting military conflicts elsewhere become surrounded by armed citizens and can rely on little, if any, national and international support to combat poaching by armed people48. Therefore, considering measures can reduce the impact of warfare on wildlife, we emphasize the intentional or inadvertent complicity of foreign powers, which should also promote policies to mitigate the detrimental environmental impacts of armed conflicts.
We conclude that armed conflicts remain a poorly understood driver of wildlife population collapses and our results indicate that although individual conflicts can have either positive or negative impacts, the overarching trend is clearly negative and the mere propagation of warzones, regardless of their intensity, is sufficient to heavily deplete wildlife populations. In the interest of preventing wildlife collapses in other parts of the world, we highlight that civil wars can vastly increase the availability of automatic weapons/ammunition which are typically used to deplete wildlife; this consequently leads to intense slaughter and major wildlife declines, especially in more accessible open habitats. This may be easier stated than done, but we conclude that policy strategies that can prevent the consequences of warfare, as shown here, remains a key conservation priority. We realize, however, that this rests on recalcitrant political will to promote robust public policies, which are rare priorities in rebuilding nation-states. It is critical to restore vertebrate community structure, but this may take many decades and require active intervention efforts. A multifaceted strategy to prevent previous war-zones from becoming “empty forests” or “empty savannas’’—severely degrading patterns of diversity, ecosystems functioning and ultimately human welfare—is therefore quintessential.
Source: Ecology - nature.com
