Birds and Climate Change | birdsclimatechange

Birds and Climate Change

As we all know, the climate is changing rapidly. According to the IPCC, the average increase in temperature from 1880 to 2012 has been estimated at 0.85°C. There is considerable spatial variation in the extent of the temperature changes, with the temperate region experiencing greater warming. Oceans are becoming warmer too, and also more acidic. In addition, polar ice caps and glaciers are melting, leading to a rise in sea levels that may put large areas of land under water.

There are multiple ways in which climate change will, and already have, affected bird populations around the globe. This page aims to summarise some of the current knowledge on this topic. If you want to learn more, there are some links supplied at the bottom of the page that provides further information.

Range Shifts

There is already clear evidence of range shifts in many bird species. Most shifts occur polewards, or up mountain-sides, to move away from warming temperatures. This is a pattern found on several continents and considering that the range shifts are almost always towards colder regions, it is likely a result of climate change. Being a mobile group of animals, birds should be able to relatively well track changes in climate by shifting their range, but there is evidence that they are not moving fast enough to track temperature changes and may thus be exposed to unfavourable climate. In addition, even though birds may be able to perfectly track their optimum temperatures, they will have to enter new areas, which may prevent challenges in form of new predators or lack of food. Completely new communities may be created as a result of range shifts. Species already living at cold temperatures, on mountain tops or close to the poles are faced with the challenges that come with suboptimal conditions, as they have nowhere to go.

Migration

Some birds species migrate seasonally, to remain at optimum conditions throughout the year. This process is also likely to be influenced by climate change. It may be that as temperatures increase, migration is not necessary in order to avoid harsher cold winter temperatures, and as migratory birds stay on in their summer habitat, bird communities change drastically, with unknown consequences. It may also be that increasing temperatures benefits resident birds who then increase in number, representing increased competition for arriving migratory birds.

Another potential issue is the loss of stopover habitats, where birds pause on their route in order to re-fuel for the rest of the journey. Coastal wetlands often form an important component of these stopover habitats, and these wetlands may become increasingly flooded as sealevels rise. Other stopover habitats may be subject to desertification or vegetation changes as a result of climate change, having a detrimental impact on the important refuelling process for migratory birds.

Furthermore, climate change also alters the seasonal timing of events, also known as phenology and further discussed below, and this means that migration, which may be timed to co-incide with abundant resources at the destination, suddenly becomes out of synch with this resource peak and as a result the birds are left with little food resources.

Lastly, climate change is expected to bring an increase in extreme weather events such as storms and droughts, which may prevent migratory birds from making their journey as the weather conditions are just too harsh.

Phenology

As previously mentioned, phenology refers to the timing of seasonal events. This can be for example the appearance of tree buds, the onset of migration or the laying of eggs. As warming temperatures in spring (or cooling temperatures in autumn) often are used as cues for the onset of these events, changing temperatures as a result of global warming are expected to alter the timing of these events. As phenology governs resource availability, the synchronicity of these events may be crucial. For example, timing the hatching of bird eggs with the availability of food for the chicks may be key to ensuring their survival.

There is evidence that the timing of these seasonal events may become increasingly out of synch as climate change progresses. For example, a study of pied flycatchers in the Netherlands found that egg hatching and the peak abundance of caterpillars were becoming increasingly out of synch, which had led to sharp declines in the population sizes of pied flycatchers (Both et al. 2005).

What does this all mean?

The processes outlined above are not the only ways by which birds are influenced by climate change, but there are multiple other ways, and probably more to be discovered. Considering the variety of forms of birds, and the variety of habitats that they occur in, they are all expected to respond differently to climate change. Climate change may be detrimental for some species, while it will have no, or even positive, effects on others. Furthermore, species do not live in isolation, and effects on any one species are likely to spread throughout the whole system, which makes it even harder to figure out how climate change really will affect nature. In addition, climate change is not only the only threat to global ecosystems, but is likely to act in concert with other forms of environmental change. All we can say is that we are having a huge impact on this planet, and large changes are needed in order to stop it.

Sources:

AFP, 2015. Climate change affecting bird migration. Available at: http://phys.org/news/2015-11-climate-affecting-bird-migration-eco-group.html

BirdLife International (2015) Climate change is driving poleward shifts in the distributions of species. Presented as part of the BirdLife State of the world's birds website. Available from: http://www.birdlife.org/datazone/sowb/casestudy/171.

Both, C., Bouwhuis, S., Lessells, C.M. and Visser, M.E., 2005. Climate change and population declines in a long-distance migratory bird. Nature 441: 81-83.

IPCC, 2014: Climate Change 2014: Synthesis Report. Contribution of Working Groups I, II and III to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Core Writing Team, R.K. Pachauri and L.A. Meyer (eds.)]. IPCC, Geneva, Switzerland, 151 pp.

WMBD, 2008. Climate change and migratory birds. Available at: http://www.worldmigratorybirdday.org/2007/index44cb.html?option=com_content&view=article&id=11&Itemid=5

Links:

Videos:

Birds and Climate Change, by the National Audubon Society:

https://www.youtube.com/watch?v=aN2-a82_3mg

The Effects of Climate Change on Birds & Bird Migration, by Eyal Bartov:

https://www.youtube.com/watch?v=044az1IwcVk

Reports:

The Messengers: What Birds Tell Us about Threats from Climate Change and Solutions for Nature and People, by Birdlife International and the National Audubon Society 2015:

http://climatechange.birdlife.org/assets/THE_MESSENGERS_FINAL_WEB.pdf

Birds and Climate Change, by WWF:

http://d2ouvy59p0dg6k.cloudfront.net/downloads/birdsclimatereportfinal.pdf

Books:

Møller, A., Fiedler, W. and Berthold, P. ed., 2010. Effects of climate change on birds. Oxford University Press.

Pearce-Higgins, J.W. and Green, R.E., 2014. Birds and Climate Change: Impacts and Conservation Responses. Cambridge University Press.