Using multi-scale spatial prioritization criteria to optimize non-natural mortality mitigation of target species

Abstract

Non-natural mortality is a major threat to animal conservation worldwide. Its origins are extremely diverse and include infrastructures that cause animal casualties. Its effects are widely felt and so prioritization criteria are necessary when implementing mitigation actions. Most of the threats causing non-natural mortality have in common the fact that they are distributed unevenly across several spatial scales. Thus, here we present a protocol for prioritizing conservation measures in: (i) population fractions suffering from high levels of non-natural mortality whose demographic effects are the most serious, and in (ii) areas with the highest risk of casualties due to heterogeneities in both spatial use by individuals and the inherent hazards of the infrastructures causing mortality. To do so, the protocol consist of 5 steps: 1) to identify sink populations over large geographical areas; 2) to identify sink areas of high mortality within target populations; 3) to identify areas intensively used by individuals in target areas; 4) to identify spatial points or individual infrastructures showing high mortality risk; and 5) using direct evidence of casualties to complete information on high-risk sites and infrastructures. To show the potential of this protocol, we use as an example the mitigation of mortality due to electrocution in Bonelli's eagle in SW Europe, where this species is of conservation concern. Thanks to the retrofitting of dangerous pylons, we demonstrate that our protocol can help restore Bonelli's eagle territories to levels that will ensure the persistence of the studied population. In addition, we show that our criteria enhance the optimization of resource investment in mortality mitigation as our criteria identify the pylons with the most devastating effects on the population. To summarize, we provide the basis for a framework applicable to many different species and scenarios whose costs in terms of mitigation actions and benefits in terms of population viability prospects can be explicitly calculated.