Climate Change and Animal Migration
Moore, Thomas T., Environmental Law
I. INTRODUCTION II. Climate Change Effects on Animal Migration A. Habitat Alteration B. Changes in Resource A variability C. Increases in Disturbance D. Changes in Phenology E. Migration Cessation F. Spatial Variability in Climate Change Effects III. Conclusion
Migrations are recurrent movements between habitats that often take advantage of seasonally productive habitat during the breeding season. (1) Migrations span a range of movements from long, cross-continental movements to comparatively short movements of a few hundred meters. Animal migrations are essential to the healthy function of many ecosystems by facilitating dispersal of plant species, cycling resources between locations, and allowing life to persist in some of the most extreme locations on earth. (2) Conditions in areas such as savannah, boreal forest, and alpine regions can be extremely harsh for much of the year, but do have brief periods of high resource productivity. (3) Through migrations, species can take advantage of these productive periods while escaping the harsh periods. (4) However, climate change may alter the dynamics of the habitats and processes on which migration depends. Due to their interactions with their environment, migrating species can be especially sensitive to climate change. (5) While there has been much work on the effect of climate change on biological systems in general, (6) few studies have attempted to gather that information and apply it to how climate change will affect migrations.
Climate change is predicted to have many varied impacts on species around the world. (7) In this Introduction, I will discuss how climate change is predicted to impact biological systems in general. In the following Parts, I will provide more detail on how those impacts are most likely to be significant to animal migrations. Finally, in the Conclusion I will describe what scientific research and management techniques are needed to confront these effects.
The most well-known impact of climate change is an increase in temperature. (8) The temperature mean and variability are predicted to rise, so the average temperature will be hotter while temperature extremes also become more severe. (9) In addition, precipitation patterns are calculated to change around the world, with much more rainfall in some regions while other areas will receive much less. (10) Projecting exactly how precipitation patterns will change in the future is exceptionally difficult, with similar global circulation models (11) predicting different results. (12) Through the interaction of temperature and precipitation changes, water availability is predicted to decrease--even if it rains more--because evapotranspiration (13) will increase with increased temperatures. (14) In addition, glaciers and alpine snow pack will melt at accelerated rates, decreasing the sources of water that have sustained mountain streams and lower elevation rivers for thousands of years. (15)
The spatial variability (16) of climate change impacts will be large. This is one reason why climate change is so difficult to manage for and predict. Some areas will become drier, others will become wetter. (17) Some areas will become much hotter, while others may change only a little. However, evidence shows that colder regions (i.e., montane and poleward regions) have been most strongly affected by climate change and will likely continue to be. (18)
The result of all these impacts will be a likely reduction in primary productivity (19) and the creation of "novel ecosystems" unlike anything in recorded history. (20) Diets will shift as the quality and type of food is altered. There will be other changes in community interactions as species composition and habitat types are transformed in reaction to climate change.
II. CLIMATE CHANGE EFFECTS ON ANIMAL MIGRATION
Climate change will affect all species, and migratory species will be confronted with many of the same climate change driven issues that nonmigratory species must confront. …