Drivers of human-wildlife impact events involving mammals in Southeastern Brazil
Graphical abstract
Introduction
Anthropogenic activities have contributed to the decline and loss of animal and plant species in almost all the terrestrial ecosystems of the Earth (Barnosky et al., 2011), and consequently contributed to a decrease in ecosystem resilience, functional integrity (Larsen et al., 2005) and the loss of associated ecosystem services (Valiente-Banuet et al., 2015). Habitat loss and degradation, overexploitation, pollution, invasive alien species and disease are the main drivers of defaunation (Dirzo et al., 2014; Pereira et al., 2012). However, other direct factors such as large, uncontrolled fires (Lewis, 2020), traffic collisions (Abra et al., 2019; Abra et al., 2021), and indirect factors, such as the expansion of urban centres without proper planning (McKinney, 2002) can add to these key drivers and amplify their effects, increasing the challenges associated with the mitigation of threats to biodiversity conservation (e.g. Grilo et al., 2010). Beyond this, each year millions of animals are killed globally as a result of accidents caused by human activities, such as road traffic collisions (Abra et al., 2019; Adania et al., 2017; Lester, 2015; Malo et al., 2004), electrocution on power lines (Hernández-Matías et al., 2015; Katsis et al., 2018; Lokschin et al., 2007) and burn injuries sustained in uncontrolled fires (Mendonça et al., 2015; Sgardelis and Margaris, 1992).
There are both conservation, practical, and ethical motivations to prioritize the prevention of such accidents. Firstly, many of these species are threatened with extinction (Hernández-Matías et al., 2015; Medici and Desbiez, 2012; Mumme et al., 2000; Pinto et al., 2020), such that the loss of these individuals represents a serious threat to already endangered populations (Diniz and Brito, 2013; Hernández-Matías et al., 2015; Medici and Desbiez, 2012). Secondly, there are human costs associated with these accidents including risks of injury or death in traffic collisions with wild fauna (Abra et al., 2019; Lester, 2015), potential damage to property and inconvenience as a result of power outages caused by electrocution events (FTI Consulting, 2016), and risk of disease transmission due to contact of wild animals with humans and domestic animals (Chapman et al., 2005; Curi et al., 2012; Thompson, 2013). Given this two-way nature, these types of accidents, together with other events such as the taking of livestock by large predators and retaliatory attacks on predators, are collectively referred to as human-wildlife impacts (Redpath et al., 2013). Finally, from an ethical viewpoint, each of these individual animals is a sentient being, and we should value its life, avoiding suffering when possible (Singer, 1990). Given this range of possible motivations, there is a need for effective strategies to minimize the likelihood of human-wildlife impact events occurring. In the case of road-traffic collisions and electrocutions, strategies commonly used include the suppression of vegetation along roadsides, use of speed bumps and speed management (Collinson et al., 2019; Lester, 2015), implementation of fences and wildlife crossing structures as underpasses, overpasses, and adaptation of drainage culverts and bridges (Malo et al., 2004; Polak et al., 2019; Abra et al., 2020), increased spacing and better insulation of power lines (Tintó et al., 2010), or alternatively installation of subterranean power lines (Richardson et al., 2017).
To ensure that mitigation measures are effective, their design requires a better understanding of the ultimate causes of the human-wildlife impact events (hereafter referred to as events). However, most studies have focussed on the proximate causes, such as travel velocity and visibility on roads (Collinson et al., 2019; Hobday and Minstrell, 2008; Lester, 2015), or the structure of power transmission lines (Dwyer et al., 2013; Tintó et al., 2010). Relatively few studies have attempted to evaluate the ultimate causes, including the ways in which natural and anthropogenic characteristics of the environment lead to increased or decreased probabilities of events occurring. Those that have examined such effects suggest that, for example, the probability of roadkill events is higher where roads pass through areas with more native vegetation (Freitas et al., 2015; Malo et al., 2004), lower in areas with intense road traffic (Grilo et al., 2015; Kreling et al., 2019), and that habitat structure has an effect, with a lower probability of roadkills in more open habitats (Kioko et al., 2015). Perhaps unsurprisingly, the density of both animals and electricity networks have been shown to be important predictors of the number of electrocution events (Katsis et al., 2018). A better understanding of how the probability of human-wildlife impact events caused by human activities varies over space and time is essential in order to design effective mitigation actions and plan for their implementation. Minimising the probability of such events not only has positive conservation impact, but also direct economic benefits, as treatments required to rehabilitate injured animals are expensive, and for those animals that cannot be fully rehabilitated, there will be permanent costs of their upkeep in captivity.
In this study, we use data on human-wildlife impact events held by the NGO Associação Mata Ciliar (hereafter, NGOMC), which receives and, when possible, rehabilitates thousands of animals each year in the state of São Paulo, in the southeast of Brazil (Fig. 1). We aim to: 1) relate spatial patterns of events of different types to natural and anthropogenic landscape characteristics, to evaluate how such characteristics may affect the risk of human-wildlife impact events occurring; and 2) determine survival rates after different types of events, as well as the likelihood that animals can be fully rehabilitated and released, as opposed to being kept in captivity, or not surviving their injuries and relate this to animal's size and to the event type. We also discuss the implications of our results in the context of actions that could help to prevent these types of human-wildlife impact events, as well as the effectiveness of rehabilitation of injured animals.
Section snippets
Study system
The NGOMC is located in the municipality of Jundiaí, in the state of São Paulo, in the southeast of Brazil (Fig. 1). The NGOMC was founded in 1987, with the aim of promoting the conservation of water resources in the state of São Paulo (Mata Ciliar, 2020). Later, biodiversity conservation and wildlife rehabilitation were incorporated as further aims (Mata Ciliar, 2020). As such, each year thousands of injured animals arrive at the NGOMC due to various causes, including human-wildlife impact
Results
A total of 4552 individuals of 56 mammal species and 44 mammal genera (Supplemental Table 2) arrived at NGOMC between 2012 and 2018, as a result of 2882 independent events. Five of these species are classified as threatened with extinction by the IUCN red list (IUCN, 2021) and 12 by the Brazilian red list (ICMBio, 2018) (Supplemental Table 2). These animals came from 126 municipalities across nine Brazilian states, though the vast majority (98%) came from the state of São Paulo where the NGOMC
Risk factors for different types of animals and human-wildlife impact events
We found that anthropogenic changes in the environment, namely the occurrence of deforestation and fires, as well as the existence of larger urban areas, influence the occurrence of human-wildlife impact events with fauna. We also found that species body size and the type of event influence the likelihood that the animal survives and fully recovers from the events.
The extent of the urban area of the municipalities was positively related to the total number of events and to the occurrence of
Conclusions
Here we identified the causes of human-wildlife impact events involving fauna, which is an important step in designing appropriate actions for the prevention and mitigation of these events. Threats arising from anthropogenic activities, such as deforestation and fires, increase the frequency of these events. We also showed the low success rate of wildlife recovery and release after incidents. This context highlights the importance of implementing mitigation measures that ensure a reduction in
CRediT authorship contribution statement
R.R. Hilário: Conceptualization, Formal analysis, Writing – original draft. W.D. Carvalho: Conceptualization, Data curation, Writing – review & editing. C. Gheler-Costa: Conceptualization, Formal analysis, Writing – review & editing. L.M.C. Rosalino: Conceptualization, Writing – review & editing. T.A. Marques: Formal analysis, Writing – review & editing. C.H. Adania: Data curation. J.S. Paulino: Data curation. P.M. Almeida: Data curation. K. Mustin: Conceptualization, Writing – original draft.
Declaration of competing interest
The authors declare that they have no known competing financial interests or personal relationships that could have influenced the work reported in this paper.
Acknowledgements
LMR thanks FCT/MCTES financial support to cE3c (UIDB/00329/2020), through national funds, and the co-funding by the FEDER, within the PT2020 Partnership Agreement and Compete 2020. RRH thanks the support of the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior—Brasil (CAPES - Process 88881.314420/2019-01). WDC thanks CAPES for post-doctoral (PNPD/CAPES) scholarships. We are grateful to the City Halls (Prefeituras), rangers of the Guarda Ambiental, firemen and policemen of the partner
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