Climate Change 2. - Where are the sandeels?

Over the summer I spent two weeks as a residential volunteer on the RSPB reserve at South Stack, Holyhead. During that time, I lost count of how many times I was asked 'Where are the puffins?'. Only once, however, was I asked 'Where are all the sandeels, then?'.

Until mid-to-late July, South Stack cliffs host to around 10,000 breeding birds; mostly guillemots, but approximately 1,500 razorbills too, along with a handful of other birds such as puffins, kittiwakes and fulmar.

Who are you calling a penguin?! Razorbills (Alca torda) on South Stack Cliffs. The guillemots and razorbills spend their lives at sea, and only venture onto land to breed. 

A large part of the diet of these seabirds during the breeding consists of sandeels; several species of slim, eel-like fish that occur in shoals that are important in linking together many trophic levels of the marine ecosystem. The primary species fed upon by bird colonies in the North Sea are the adult lesser sandeels (Ammodytes marinus) which, like all sandeels, burrow into soft sandy substrates with which they are closely associated. Their distribution is therefore restricted to areas in which such substrates are found, and as a result these fish are unable expand their ranges into deeper waters to deal with the threats they may face (Scottish Gov, 2010).

A reduction in the sandeels available with not only effect species of seabirds -Kittiwakes in particular-, but also marine mammals such as harbour porpoises (MacLeod et al, 2007) and up to 10 species of predatory fish (van Deurs et al, 2009). Sadly, sandeel populations have been declining in number, and this in turn has been linked to a reduction in sea-bird populations which struggle to feed themselves and their young. Between 1986 and 2011, the number of seabirds breeding around Scotland decreased by 53%, and the decline is believed to be due to a drop in sandeel availability (Herald Scotland, 2012).

So, where are all the sandeels going?

The population decline of the sandeels has been linked to two anthropogenic causes:

• Climate change, resulting in a warming of the UK coastal waters since 1980 of up 1°C per decade (Wanless et al, 2010).
•  Over-fishing for commercial purposes, such as for fish-meal feed and fertiliser.

Sandeel population decline has been correlated with rising sea temperatures by several authors (Wanless et al, 2010) (Heath et al. 2012). As the seas warm, the cold-water zooplankton that the sandeels feed upon are replaced by less nutritious warm-water varieties (Wanless et al, 2010). Though the cold-water species are still found in cooler, deeper waters, the habitat restriction of the sandeels means they cannot follow the cold-water zooplankton as they migrate (Heath et al. 2012). As a result, the sandeel populations experience a decline.

Rising sea levels are also thought to be posing a threat to the sandeels, though overall the effects of anthropogenic climate change on Ammodytes is not fully understood, and research is still ongoing as a result.

Whilst over-fishing is not thought to be the primary cause of sandeel decline, it makes it harder for the climate-hit sandeels to fight back. In turn, this affects seabirds; Sandeel exploitation has been linked to declining kittiwake colonies near to fishing grounds.

Plans were announced in November 2012 to halt the decline in seabird numbers (Scottish Seabird Centre). One of these plans involved the inclusion of sandeel habitats in the Scottish Government's Marine Scotland agency's network of Marine Protected Areas where there are imposed fishing limits. It is hoped that these fishing limits will halt the decline in sandeel numbers, which in turn is anticipated to stem the decline in seabird populations.

Climate Change 2. - Biological Invasions Seminar Summary

First off, I'm going to apologise for the crazy amount of posts this week. I just wanted to post this whilst everything was still fresh in my mind. Secondly, this isn't 100% related to birds, as you'll see, but I thought it might interest those studying Geog3057.

On Wednesday I attended a small seminar given at UCL by Franck Courchamp, a specialist in population dynamics and conservation biology from Université Paris Sud. The talk was on 'Interactions between Climate Change and Biological Invasions' and here I'm giving a quick summary of what was said.

Myrmica rubra; the European Fire Ant (aka. Common Red Ant) - by Tim Keppens on Flickr.

Biological invasions are the second greatest threat to biodiversity; they also impact upon the economy and society. Will climate change effect biological invasions? Will it make them more, or less, of an issue in the future?

Courchamp's research can be roughly divided into two sections; the effect that climate change will have on invasive ant species, and the effect it will have upon the IUCN's 100 of the World's Worst Invasive Alien Species.

Climate Change and Invasive Ant Species

• Over 200 of the ~1200 described species of ant (family; Formidae) are found outside of their native range. Some of these species can be classed as 'exotic' (i.e. not native, but not invasive). 19 of these species, however, are classed as highly invasive; 5 of them are present of the '100 of the World's Worst-' list.
• Ant invasions have important consequences for biodiversity; they may remove native species and other arthropods. They also effect mammals, birds, and other animals, and can impact seed dispersal and pollination by doing so. They also affect us; Red Imported Fire Ant (Solenopsis invicta) causes a total economic loss of around $1 billion per year, as well as roughly 100 deaths from anaphylaxis (severe allergic reaction).

Using climatic models, will invasive ant species increase their range and 'invasive-ness'?

• Some ants (5 species) will benefit from climate change, and will become more able to invade new regions. Amongst these are the Asian Needle Ant (Pachycondyla chinensis), Singapore Ant (Monomorium destructor) and European Fire Ant (Myrmica rubra).
• HOWEVER, many species are projected to freeze or decrease in their invasiveness (7 decreases and 3 remain 'stable'). 3 of the decreasing species are amongst the 'World's Worst'. 
• So, overall, the general global trend seems to be that future climate change will decrease the invasiveness of ants. 
• But don't start the party just yet! When we look at and compare the regions that these invasions are decreasing and increasing in, we get a more grim picture. Though the global trend in the future is to decrease, two-thirds of species show a strong increase in the world's Biodiversity Hotspots which, though they only cover 2.3% of the Earth's land area, contain high numbers of endemic species. 

Climate Change and the 100 of the World's Worst...
Having looked at invasive ants, Courchamp and his PhD students repeated the models, but this time did so for all of the '100 of the World's Worst-'. Would the results be worse, or better?

•  Aquatic and terrestrial invertebrates, as well as terrestrial plants, amongst others, showed an increase in their invasive range. Europe and South America in particular showed a greater risk of being invaded with future climate change.
• Amphibians and birds, amongst others, showed a decrease in their invasive range with climate change. As with the ants, their was a general global decrease in invasiveness. 
• However, as it had been with ants, the picture was different when Biodiversity Hotpsots were focused upon. With climate change, these hotspots were more likely to be invaded in hue he future, and some are more susceptible than others. Polynesia, for example, is at risk from 35 of the 'World's Worst'. 

In the words of Franck Courchamp, the overall pattern is "a lot of invasions everywhere". Even though some species show a decrease in their distribution, as most are predicated to increase their distribution in the places that are most at risk we can be fairly confident in saying that climate change will not suppress biological invasions. 

Journals referenced in the talk:

• Increase in Quantity and Quality of Suitable Areas for Invasive Species
• Impacts of Climate Change on the Future of Biodiversity
• Will Climate Change Promote Future Invasions?

Climate Change 1. - The Big Picture

Being perfectly honest, this is really just an overview; were I to address every impact that climate change has had upon birds, I would be here for a long, long time. Whilst I can and will focus on the finer points in my future posts, here I simply aim to provide a stepping stone. The topic of Climate Change is a long debated one, and the effect that our activities have had upon the climate is one of the reasons why many believe we're entering a new geological time; the Anthropocene.

What is Climate Change, and how do we know it is happening?
In short, Climate Change is a large-scale, global change in patterns of weather and temperature trends over time. As a result of shifting climate zone boundaries, climate change also results in a shift of biodiversity over time.

Athabasca Glacier in Canada is just one of the world's many retreating mountain glaciers that make it hard to deny that our planet is has been warming over the last century - by Maggie T on Flickr

Climate Change can be natural; the earth has experienced both cool periods where ice has been present over the poles, and warmer ice-free periods. Whilst the exact mechanisms for natural climate change are not fully understood, it is believed changes in the earth's orbit (Milankovitch Cycles) (British Geological Society) (Wikipedia, 2013) play a large role. This sort of climate change, however, takes place over thousands of years. Since the beginning of the 20th century global temperature has risen 0.8°C (1.4°F) (UK MetOffice) (US EPA) (Koronowski, 2013). This rapid change is above and beyond natural climate change (IPCC, 2007) and has been attributed to human activities; primarily an increase in atmospheric CO2 (from 280ppm before the industrial revolution (IPCC, 2007) to the present value of over 390ppm)(CO2 Now) through the burning of fossil fuels.

This rise in temperature has in turn caused a shift in global precipitation pattens (US EPA). Whilst there has been increased rain observed in the northern hemispheres mid-latitudes, other areas of the globe have suffered increasing drought  (UK MetOffice). Climate change has also brought with it a rapid retreat in mountain glaciers (Oerlemans et al, 1998) (Kaser et al, 2003) , a decline in sea ice and continental ice sheets, and a rise in sea level (Rockström et al, 2011).

Threatened by climate change and stronger, more frequent El Niño cycles; the critically endangered Waved Albatross (Phoebastria irrorata), a migratory sea-bird who's population is believed to have declined by up to 19% in the past 84 years (BirdLife, 2013) - image by Victor Burolla on Flickr

How does climate change impact upon birds?
There is compelling evidence that Climate Change has had a large impact on the behaviour, breeding patterns, breeding ranges (Araújo et al, 2005) and migration patterns of birds (Nature Canada). Earlier springs in northern hemisphere have been associated with an earlier arrival and breeding of birds, and in turn an earlier autumn and winter migration of juveniles (Crick, 2004).

For those birds that don't migrate to warmer climates, the harsher, colder winters may pose the threat of starvation and freezing as they require an increased energy expenditure for birds to keep warm (Crick, 2004). In turn, this could impact breeding success.

Other threats posed to birds, both migratory and non-migratory, include the loss of habitat and food (National Geographic, 2013). Whilst some areas of the world are becoming dryer and suffering from drought, other areas are becoming more 'hospitable'; in Alaska trees are now appearing on the formerly tree-less tundra, and deciduous trees are beginning to replace mountain conifers (O'Hara, 2011) . Whole ecosystems are changing rapidly, and populations of birds unable to adapt to these changes may decline rapidly.