1. Introduction
The escalating growth of the human population has increased demands for natural resources and fossil fuels [
1]. During the 21st century, the human population has increased from 1.65 billion to 6.5 billion people, with a potential of reaching 8 billion people by 2025 [
2,
3]. As a result, human-dominated landscapes have intensified natural habitat degradation and fragmentation, and wildlife populations are now in regular competition with people for resources, thus eliciting human–wildlife conflict (HWC). In this study, HWC denotes any instance in which the resource demands of humans and wild animals overlap, spurring competition for food, space and water and thus creating tension between people and wildlife [
4,
5]. In addition, HWC threatens food security of people and the well-being of both people and wildlife [
5].
Human–wildlife conflict is a global issue, afflicting both developed and developing countries [
5,
6]. Characteristics of HWC incidences are dependent on the type of resident wildlife in the region and the farming practices that are typical for that area. Wildlife in North America and Europe have been either extirpated or have experienced major geographic range collapses through hunting and persecution by people [
5]. In most developed countries today, HWC is typified by large mammalian carnivores and commercial farmers [
7,
8] because of extant wildlife assemblages and farming practices. Examples include the brown bear
Ursus arctos, lynx
Lynx lynx, gray wolf
Canis lupus and wolverine
Gulo gulo, all of which predominantly depredate commercially farmed sheep
Ovis aries and/or cattle
Bos taurus [
7,
8]. Such developed countries include Italy, Norway [
8,
9], the United States of America (USA) [
7], Canada [
10] and Australia [
11,
12].
Developing countries, such as India [
13], Cameroon, the Central African Republic, Congo, Equatorial Guinea, Gabon [
14], Uganda [
15] and Bhutan [
16], experience a wide variety of depredation by problem animals when compared with developed countries [
6]. Examples include regular crop-raiding by non-human primates (hereafter primates), mega-herbivores (large-bodied herbivores), omnivores (e.g., wild boar
Sus scrofa) and small mammals (e.g., cane rat
Thryonomys swinderianus) [
14,
17]. Poultry depredation by mongoose
Herpestes spp. and jackal
Canis spp. are typical occurrences in Tanzania [
18]. Human and livestock depredation in developing countries due to carnivores, for example, tiger
Panthera tigris and the snow leopard
Uncia uncia in India, leopard
Panthera pardus in Zimbabwe, Tanzania and Pakistan and lion
Panthera leo, are major sources of conflict [
19,
20]. Farmed game depredation by African wild dog
Lycaon pictus (Gusset et al., 2008; Lindsey et al., 2005) are also common in developing countries, such as Zimbabwe [
21,
22], Botswana [
23] and South Africa [
21,
22]. These occurrences suggest that the geographic distributions of wildlife populations together with farming practices are important predictors of HWC.
Currently, Africa has over 3000 protected areas (PAs), with approximately 50 biosphere reserves (i.e., PAs established to conserve the biological and cultural diversity of a region). Africa houses the world’s largest reservoirs of wild animal populations in terms of density and diversity compared with the rest of the world [
24,
25]. Some scholars believe that these PAs were established at the cost of local livelihoods [
25,
26,
27]. In the late 19th century, corresponding to outbreaks of rinderpest, unregulated hunting of wildlife and indigenous habitat clearing for farmland [
28], urgent efforts to conserve natural resources and establish PAs were made by colonial governments [
25,
29]. It is estimated that about 50% of PAs worldwide have been established on land traditionally occupied and used by indigenous people [
29]. Throughout Africa, thousands of indigenous people were evicted to accommodate the establishment of PAs [
25,
27,
30] and compressed into impoverished communities bordering PAs, and many of these communities exist still today [
26]. Currently, the livelihoods of local human communities residing on the edge of these PAs often involve the direct exploitation of natural resources [
26], bringing the communities into conflict with wildlife and park authorities.
According to the Food and Agricultural Organization (FAO) of the United Nations [
31], Sub-Saharan Africa is dominated by smallholder subsistence farms, cultivating a mixture of crops corresponding to different soil and water regimes. Human pressure on soil health has left a third of all soils on which crop production depends degraded worldwide [
32]. In Sub-Saharan Africa, ~180 million people are affected by land degradation [
31,
32] due to damaged soils that impede crop yields. Additionally, African pastoralist communities mostly live in remote and underdeveloped areas that are plagued by drought and disease [
3]; therefore, these areas are associated with high levels of vulnerability to food insecurity [
32]. Pastoral areas in Africa occupy about 40% of Africa’s land mass, with variations between countries [
3]. Generally, pastoral areas are less suitable for crop production, and livestock husbandry remains the most common farming practice in arid regions of Africa [
32].
South Africa is undergoing transition and reform with a contentious and distinct socio-economic and political history of racial segregation under the apartheid government [
27,
33]. South Africa is also a unique country of dualities in which first world, wealthy and stable industries and third world, underdeveloped sectors occur concurrently, and this is exemplified in the agricultural sector that comprises subsistence households and commercial farmers [
34] farming within the same geographic area. Approximately 20% (2.9 million) of all households in South Africa are subsistence households [
35] that are compressed into racially segregated settlements in poor farming areas [
25,
27]. Commercial farmers dominate in particular provinces within South Africa, such as the Free State with ~10,000 farms, the Western Cape with ~8300 farms and the North West Province with ~7500 farms [
35]. In contrast, Ebedes [
36] reported that the approximately 7000 privately owned game farms in South Africa occupy 16 million hectares of land. Importantly, while commercial agriculture generates R30 billion (~US$1.8 billion, where one South African Rand (ZAR) = US$0.062) in profits annually, the game farming industry turnover accumulated R105 million (~US$6.5 million) in the same period. In comparison, many of the households involved in subsistence agriculture, which far outnumber commercial and game farms, have limited income and depend on their farming efforts to ensure food security [
35].
Most of the land in South Africa is only suitable for grazing (84 million hectares) and, due to soil aridity [
37], only 13.5% can be used for crop production [
25]. Commercial farming comprises livestock farming, game farming, field crops and horticulture [
25]. Livestock keeping in South Africa consists predominantly of poultry and egg production, followed by red meat and dairy production, while crop and horticulture production predominantly consist of maize
Zea mays, sugar cane
Saccharum spp., potato
Solanum tuberosum, wheat
Triticum aestivum, and deciduous and citrus fruit [
25,
31].
In South Africa, several abiotic factors challenge farming efforts, namely decreasing soil fertility, low rainfall, increasing soil salinity and greenhouse gas emissions from livestock. Drought and famine have had devastating effects in southern Africa periodically [
37]. The most severe droughts for the summer rainfall region of South Africa occurred in 1982/1983, with crop loss amounting to about R2.2 million (~US$136,700), and resulting in a drop in the Gross Domestic Product (GDP) by 7%. Similar impacts on GDP occurred in the 1992 drought [
38]. During those periods of environmental stress, incidences of HWC also intensified. For example, the alleged damage caused by Chacma baboon
Papio ursinus to timber plantations in South Africa increased during the 1982/1983 droughts, when these baboons utilised alternate food sources such as commercially farmed pine
Pinus spp. trees. These incidences did not re-occur until the 1993/1994 droughts [
39,
40]. Environmental and climatic factors, therefore, increase opportunities for HWC, which manifest into crop and livestock damage [
39,
40].
In South Africa, approximately 30% to 55% of poor, local community members reported HWC occurrences due to problem animals from neighbouring PAs [
41]. Crop raiding by elephant
Loxodonta africana and baboon and livestock depredation by lion and spotted hyena
Crocuta crocuta were reported [
41], and sporadic incidences involving large carnivore attacks on people were also documented [
41]. Frequent episodes of crop-raiding were associated with harvest time, the most critical and vulnerable period for those impoverished households [
41]. These findings indicate serious conservation and socio-economic issues that warrant further investigation.
There have been several international efforts to conserve cultural and natural amenities in developed countries, to increase the popularity of a destination through scenery and outdoor recreation [
42]. Wildlife densities in such developed countries, however, remain low due to historical extirpations and several land-use changes (mining, farming, industrialisation) [
43]. In contrast, developing countries in Africa contain 25% of the global mammal species, including about 80 species of antelope and >2000 bird species. In addition, Africa is home to 24% of the 34 global biodiversity hotspots [
44]. South Africa, in particular, houses the third highest level of biodiversity globally [
25] and presents a unique scenario to investigate HWC due to the prevalence of commercial farmers and local subsisting communities competing with PAs for critical natural resources.
The aim of our study was to investigate the occurrence of HWC globally and subsequently in relation to South Africa in order to assess common trends in vulnerable human populations, their farming practices and vulnerable wildlife guilds (e.g., carnivores and mega-herbivores). We adopted a broad approach because no study has previously considered HWC at a global scale or even considered the plight of affected communities in developing countries. We conducted a meta-analysis of published scientific literature from 1994 to 2015 indexed through the Institute for Scientific Information (ISI). Specifically, we (1) catalogued the global distribution of HWC from scientific publications; (2) assessed the numbers and types of HWC incidences experienced by different types of people (i.e., subsistence farmers, commercial farmers and local communities) in developed and developing countries; (3) identified damage-causing animals (DCAs); and (4) gauged the vulnerability of DCA species. We made three predictions: (1) Subsistence farmers/local communities would experience a higher number of depredation incidences than commercial farmers. This might be due to local communities’ and subsistence farmers’ close proximity to PA edges and the inability of poor households to afford wildlife-proof deterrents. (2) Mega-herbivores, primates and carnivores would feature prominently as DCAs in the literature. This might be due to their broad geographic distribution and their ability to transgress PA boundaries. Although small mammals can transgress boundaries, mega-fauna (large-bodied mammals) cause damage that is more noticeable over a short period. (3) Farmers in developing countries would be affected by a wider diversity of DCAs than farmers in developed countries. This might be due to the prevalence of dense and diverse wildlife reservoirs in, for example, Africa and Asia, and the inability of poor communities to afford fencing for their gardens and pastures.
6. Glossary of Terms
Apartheid. An official government policy of racial segregation formerly practised in South Africa, involving economic, legal and political discrimination against black individuals into second-class citizens who were restricted geographically, educationally, socially and professionally [
66].
Commercial farmer. A farmer or enterprise that cultivates crops or produces livestock or game for sale with the objective of making a profit [
31].
Conflict profile. A measure of the vulnerability of people and farming commodities to human–wildlife conflict based on the number of HWC cases reported in the published literature for such groups of people, in combination with the number of low-, moderate- or high-scale conflict species that commonly affect such groups of people.
Crop-raiding. The feeding or destruction of cultivated food by wild mammals and/or birds that causes significant loss of food and income to farmers [
5].
Damage-causing animal (DCA). A free-living mammal or bird for which there is considerable evidence that it causes loss to livestock or game, or causes excessive damage to cultivated crops or poses a threat to human safety [
5].
Depredation. The consumption of agricultural resources (crops, livestock and game) by free-living mammals and/or birds [
5].
Developed (first world) country. An industrialised country with a well-developed economy and an advanced technological infrastructure relative to other less industrialised countries [
12,
31].
Developing (third world) country. A nation with an underdeveloped industrial base that is characterised by people with reduced life expectancy and lower income when compared with developed nations [
12,
31].
Edge. A boundary or interface between a protected area and a landscape element (human settlement or farmland) [
85].
Food security. The state in which all people at all times have access to sufficient, safe, nutritious food to maintain a healthy and active life [
31].
High-scale conflict species. Free-living mammals or birds that frequently (appear in five or more scientific papers according to Inskip and Zimmermann [
46]) attack people and/or recurrently depredate livestock or crops, resulting in frequent retaliatory killings.
HWC hot spot. A biogeographic region in which significantly high incidences of human–wildlife conflict occurs [
5].
Local community. People living adjacent to protected areas or reserves, who may or may not subsist through farming [
26].
Low-scale conflict species. Free-living mammals or birds that rarely (appear at least once in a scientific publication according to Inskip and Zimmermann [
46]) attack people, seldom depredate livestock or crops and rarely experience retaliatory killings.
Moderate-scale conflict species. Free-living mammals or birds that rarely (appear in two to four scientific papers according to Inskip and Zimmermann [
46]) attack people but may frequently depredate livestock or crops and experience frequent retaliatory killings.
Problem animal. A free-living, native wild mammal or bird whose natural behaviour, temperament or habits brings it into conflict with humans [
5].
Protected area (PA). A biodiversity conservation area that receives protection due to the presence of indigenous fauna and flora that offers great ecological value [
48].
Subsistence farmer. A farmer whose products are intended to provide for the basic needs of the farmer and his/her family with little surplus for marketing, bringing no profit (i.e., allowing for only a marginal livelihood) [
31].
Wildlife. Undomesticated terrestrial vertebrate and invertebrate animals.