Conserving a moving target: planning protection for a migratory species as its distribution changes.
Abstract
Conservation of declining migratory species is a challenging task, as the factors that may have determined their past distribution may not determine their current and future distribution. Saiga antelope Saiga tatarica populations have massively declined due to poaching. The species is now beginning to recover in Kazakhstan and protected areas are being implemented. Using 25 years of aerial monitoring data, we identified changes in the spring distribution and predicted densities of saiga to prioritize areas for protection under scenarios of climate change together with changes in disturbance and population size. Conserving the spring distribution is critical as spring calving aggregations are of particular importance to population viability. The current distribution is strongly influenced by disturbance, whereas climate had a stronger influence in the past. The area of highly suitable habitat has halved and become fragmented in the last decade. The existing and proposed protected areas are relatively complementary and perform well under most scenarios of future change. However there is a need to widen the geographical scope of protected area planning if potential future high suitability areas are to be effectively protected. Climate change interacts with other factors to determine the distribution of suitable habitat within and outside protected areas. Scenarios in which conservation has increased saiga population size and density tend to show limited impacts of climate change, while scenarios in which the saiga population fails to recover and disturbance continues show, worsening patchiness and reduced suitable habitat. Synthesis and applications. We provide evidence for changing distribution and density of a migratory species over a large spatio-temporal scale, and suggest that future distribution may be more constrained and spatially heterogeneous. These results have important implications for designing future conservation measures for migratory species, such that areas that robustly show high suitability under a range of potential scenarios of change can be included in protected area expansion plans. Protected area placement based only on current, rather than projected distribution risks wasting opportunities for proactive conservation, particularly for a highly disturbed, recovering species likely to be affected by climate change.