The scope and extent of literature that maps threats to species globally: a systematic map
Background
Human activities are driving accelerating rates of species extinctions that continue to threaten nature’s contribution to people. Yet, the full scope of where and how human activities threaten wild species worldwide remains unclear. Furthermore, the large diversity of approaches and terminology surrounding threats and threat mapping presents a barrier to understanding the state of knowledge and uptake into decision-making. Here, we define ‘threats’ as human activities and direct human-initiated processes, specifically where they co-occur with, and impact the survival of, wild species. Our objectives were to systematically consolidate the threat mapping literature, describe the distribution of available evidence, and produce a publicly available and searchable database of articles for easy uptake of evidence into future decision-making.
Methods
Four bibliographic databases, one web-based search engine, and thirteen organisational websites were searched for peer-reviewed and grey-literature published in English 2000–2020. A three-stage screening process (title, abstract, and full-text) and coding was undertaken by two reviewers, with consistency tested on 20% of articles at each stage. Articles were coded according to 22 attributes that captured dimensions of the population, threat, and geographic location studied in addition to methodological attributes. The threats studied were classified according to the IUCN Red List threat classification scheme. A range of graphical formats were used to visualise the distribution of evidence according to these attributes and complement the searchable database of articles.
Review findings
A total of 1069 relevant threat mapping studies were found and included in the systematic map, most conducted at a sub-national or local scale. Evidence was distributed unevenly among taxonomic groups, ecological realms, and geographies. Although articles were found for the full scope of threat categories used, most articles mapped a single threat. The most heavily mapped threats were alien invasive species, aquatic or terrestrial animal exploitation, roads and railways, residential development, and non-timber crop and livestock agriculture. Limitations regarding the English-only search and imperfect ability of the search to identify grey literature could have influenced the findings.
Conclusions
This systematic map represents a catalogue of threat mapping evidence at any spatial scale available for immediate use in threat reduction activities and policy decisions. The distribution of evidence has implications for devising actions to combat the threats specifically targeted in the post-2020 UN Biodiversity Framework, and for identifying other threats that may benefit from representation in global policy. It also highlights key gaps for further research to aid national and local-scale threat reduction. More knowledge would be particularly beneficial in the areas of managing multiple threats, land-based threats to marine systems, and threats to plant species and threats within the freshwater realm.
Keywords
Threat mapping, Biodiversity conservation, Evidence synthesis, Species extinctions, Human footprint
Background
The rate of anthropogenic biodiversity loss far exceeds the background rate of species extinctions. Global targets for biodiversity acknowledge this, nevertheless progress towards targets has been poor. There is now a reasonable understanding of what human pressures threaten the survival of species. However, information on where these threats are impacting species is needed to coordinate conservation actions and threat abatement efforts. Herein, threats are defined as human-driven pressures specifically where they co-occur with, and threaten the survival of, native wild species. There is a large number of studies that map either distributions of threatened species or human-driven pressures alone. This makes it difficult to identify research that has investigated the spatial distribution of the threats themselves. Additionally, the high variability in approaches taken in these studies promotes a high risk of duplication and diversity among the findings. This variation, and the lack of studies directly mapping threats, limits the utility of threat mapping studies for conservation planning and informing policy. Therefore, a systematic consolidation of the literature is necessary to identify where knowledge is lacking, and where sufficient evidence exists for synthesis of the collective findings.
Methods
This protocol details the process for a systematic mapping exercise aiming to identify studies that map threats to species across the world. For a study to be included it should present spatially explicit data on both the occurrence of species and the human-driven pressures threatening them. A range of peer-reviewed and grey literature repositories will be searched in English for literature published 2000–2020, followed by one iteration of backward snowballing. A three-stage screening process will be implemented before data are extracted on geographic coverage, taxonomic extent, and threats investigated. Data on the threats studied will be categorised using the threat classification scheme used by the IUCN Red List to allow comparisons among studies and to identify unrepresented threats. The extracted data will be analysed and visualised to describe the extent of existing knowledge. The resulting database of studies, findings from descriptive analyses, and accompanying narrative synthesis, will be made publicly available.