Conserving a moving target: planning protection for a migratory species as its distribution changes

Abstract

Summary1. 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. 2. 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. 3. 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. 4. 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.

What are the roles of species distribution models in conservation planning?

“…For example, the scale of a species' environmental niche is often small relative to outputs of climate models and undetected climate refugia will exist within these future landscapes (Weins & Bachelet 2010). In addition, anthropogenic stresses may have complex interactions with projected changes in climate parameters (Singh & Milner-Gulland 2011) and the uncertainty values of critical parameters makes future predictions challenging for some species (Carvalho et al 2011). Of particular note is that the persistence of organisms in future landscapes depends partially on their ability to migrate into newly suitable habitats, abilities that are poorly understood for most species (Franklin 2009(Franklin , 2010.…”

A multi-method approach to delineate and validate migratory corridors

“…Some corridors are used mainly for connectivity, while others have functional uses, such as habitat for short stop-overs and even longer foraging 460 bouts (Sawyer and Kauffman 2011). Given the ecological significance of these different behavioral states, efforts to delineate corridors should ideally incorporate methods that can differentiate these behaviors and functions, though this can be difficult with ground-based observations because the timing of migration can vary substantially with the timing of rainfall, and is thus difficult to observe (Holdo et al 2009;Singh and Milner-Gulland 2011). In our 465 study, visual detections did not reveal which behavioral state (migratory versus sedentary) individuals expressed at the time of observation.…”

“…Long-distance migrations provide large-scale ecological benefits and services such as nutrient transfer, soil fertilization, and seed dispersal (Hamilton et al 1998;Holdo et al 2009;Estes 2014). However, migrations are in precipitous decline globally 35 because of rapid environmental change in many of the landscapes in which they still occur (Bolger et al 2008;Harris et al 2009;Singh and Milner-Gulland 2011). The linear shape of many corridors (Sawyer et al 2009) make migrations particularly sensitive to the effects of habitat loss and fragmentation, particularly in areas that act as natural bottlenecks such as valleys or passes (Morrison and Bolger 2014).…”

Interactions between human behaviour and ecological systems

“…For example, Singh & Milner-Gulland [31] examined the effectiveness of current and planned protected areas in covering areas of predicted high probability of the presence of a critically endangered species, the saiga antelope (Saiga tatarica) within a landscape in Central Kazakhstan. The scenarios included potential climate change plus conservation success (a large population of the species in substantial herds) or failure (antelopes heavily poached, keeping away from settlements and a low population in fragmented herds).…”