Seabirds and wind - the consequences of extreme prey taxis in a changing climate

Seabirds and wind - the consequences of extreme prey taxis in a changing climate

Issued: Fri, 06 Nov 2015 11:37:00 GMT

Summary

As the world’s climate warms due to the emission of greenhouse gases, the distribution and population sizes of the organisms that make up ecosystems are changing. For example, some European songbirds are expanding their ranges northwards, while others are declining. These effects are of concern not only from a species conservation perspective but because healthy ecosystems provide services vital to humanity. For example, plants produce the oxygen we breathe and insects pollinate plants, enabling food production. As such, there is an acute need to forecast the responses of organisms to climate change so that they can be mitigated in an effective and timely manner.

My proposed fellowship concerns one group of animals that may be particularly vulnerable to climate change: albatrosses, petrels and shearwaters (or simply, ‘petrels’). These large-to-medium sized seabirds are remarkable for their ability to fly vast distances in search of food. For example, great shearwaters migrate across the equator each year, allowing them to exploit summertime peaks in food abundance in both the North and South Atlantic. Along with other large predators, like whales and sharks, feeding petrels congregate in so called hotspots caused by the ocean circulation patterns. Petrels are able to travel rapidly between these hotspots and their breeding colonies because of their ability to use the wind to fly. This, however, means that their movements are limited by prevailing wind patterns: Like the sailing ships of old, they need to avoid headwinds and areas of calm. Global wind patterns are forecast to change markedly as the world warms. For example, wind speeds in the ‘horse latitudes’, a belt of already light winds in the sub-tropics, are predicted to decline, while those at temperate latitudes will increase. At the same time, as the oceans warm, the distribution of the fish, squid and crustaceans that petrels feed on is predicted to shift towards the poles. While these changes could benefit some petrels, they may harm others. For example, during migration, great shearwaters could become becalmed in mid-ocean, where food is scarce and the chances of starvation high.

These impacts may have wider implications because, like plants and insects, petrels provide some important ecosystem services. For example, by depositing nutrient-rich guano in their colonies they support entire ecosystems on some islands. Less is known about related mechanisms in the sea but studies on large whales, which have similar diets to petrels, give some clues: They suggest that by recycling or transporting nutrients, seabirds stimulate the growth of phytoplankton, the tiny green algae that form the base of the marine food pyramid. Phytoplankton are also important because they draw carbon dioxide out of the atmosphere, slowing the rate of climate change.

Despite the threats posed to petrels by climate change there are some large gaps in our understanding of their lives. To-date, the majority of research on these species has been carried out in very remote areas, like the Southern Ocean, which surrounds Antarctica. In contrast, remarkably, little is known about the lives of petrels in the deep Atlantic, despite the fact that this ocean is bounded by some of the world’s most developed nations. The aim of my fellowship is therefore to use the Atlantic as a laboratory in order to determine how petrels have been affected by recent changes in the climate; how they affect phytoplankton growth and carbon dioxide levels; and how they may respond to future climate change. I will achieve this by recording the movement, behaviour and diet of petrels at sea using miniature loggers and ship-based sampling. I will then combine these data, using computer models, with data on wind and ocean conditions and petrel population changes, in order to predict how petrel movements, population sizes and ecosystem services will change in the future.


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