Declines in the abundance of vertebrate wildlife populations are generally well documented and the main drivers of these declines are also known, though correct attribution and estimating the extent of their impact can be difficult. Currently much of the communication within the Living Planet Report (LPR) – one of the key WWF tools for describing changes in the abundance of wildlife populations – involves reporting population changes and inferring the reasons for the changes, rather than understanding the chain of effect from human action through to habitat changes and the subsequent impacts on biodiversity. In addition, little focus is currently given within the LPR to advocating solutions and measuring the effectiveness of human actions to halt biodiversity declines and restore wild habitats.
Only by improving our understanding of the mechanisms leading to biodiversity decline and by testing solutions and assessing their costs and benefits can we move away from merely documenting declines, and towards a new conservation paradigm with human actions to reverse the loss of wild places and species placed firmly at the centre. One way to begin to work towards this goal is to develop new indicators that can measure the presence of drivers of change (Exposure), predict the related responses of biodiversity to those drivers (Sensitivity); and assess the impact of conservation interventions in remediating biodiversity loss from the identified drivers (Solution). Most existing data, however, are correlational and not designed to compare across sites or among interventions. Here we propose field studies, explicitly designed to capture information on pressure, biodiversity status and response to conservation effort within a framework that allows robust comparisons to be made between sites, and allow inferences to be made that go beyond the scope of the individual study.
Each field site will comprise a linked set of landscape-scale studies across a pressure gradient and/or a paired sampling scheme examining options for conservation intervention (schematic below). For example, in temperate or tropical forests the pressure gradient may be increasing exposure to deforestation. As forest cover is lost through clearing or fragmentation, the response metric (mammal community abundance, as measured through occupancy) also declines.
Through placing field sites along an identified gradient of forest loss, we can thus evaluate the shape of the relationship between forest loss and mammal community abundance – i.e. how much mammal occupancy declines for a quantified increase in deforestation. Multiple relationships may also be identified within field studies. The relationships identified can provide good information for conservation management. For example, for groups of species which are currently in low pressure sites but which are absent from sites facing higher pressure in a trajectory (e.g. purple and coral lines in schematic), there is great advantage in intervening early, for example prioritizing conservation at pristine/ low degradation sites before declines can occur. Across all field sites the completion of the first survey period in year one will enable a space-for-time (STS) approach to investigate the response of mammals to degradation (STS: a form of modelling used to infer past or future trajectories from contemporary spatial patterns. Repeated surveys over a 5+ year timeframe will subsequently enable quantification of temporal lags in response, as well as scope for methodological developments in the rapidly progressing fields of camera trap and acoustic monitoring. Data collected over multiple years can also feed into the LPI, broadening the taxonomic and geographic coverage or be used to create complimentary indices to the LPI (e.g. acoustic indicators).
A schematic to illustrate the potential differences in response of taxa (e.g. abundance) to varying levels of human pressure that we will quantify through the Biome Health Project.