Meeting report – Climate change and coastal birds
A joint BOU/ECSA (Estuarine & Coastal Studies Association) conference
University of Hull, 22-24 March 2002
by David T. Parkin
Approximately 100 delegates from seven countries met for the weekend to discuss the effects of climate change upon bird populations in general, and coastal species in particular. The scientific component of this generally excellent conference was organised by Mark Rehfisch (BTO).
The meeting began with a brilliant BBC film, setting the scene for the weekend by showing how rapidly parts of the planet are being changed by rising temperatures, and how this is generally detrimental to the local wildlife.
Saturday morning opened with the President, Ian Newton, introducing Sir Fred Holliday who reminded everyone that global warming is real and human-driven. He reviewed the problems of an inexorable rise in temperature and sea level, in particular, the displacement of over 150 million people increasing competition for space, clean water and energy. The problems will be political and economic, and he suggested that industry was likely to emerge with solutions more rapidly that governments. There then followed a trio of talks that described the actuality of global warming (Hulme & Watkinson), and its consequences, both socio-economic (Knogge, Schirmer & Schuchart) and geomorphologic (Pethick & Crookes). The temperature of both sea and land is rising, predicted to result in a sea level rise of 60cm in 100 years, due to melting ice-caps and thermal expansion. Flooding of low-lying areas will increase, with asset losses exceeding local economic productivity. Not only will land be flooded, but tidal and riverine flows will change, leading to the destruction of mud-flats, erosion of salt marshes and other major changes to the inter-tidal zone. Theorists are now modelling these effects, testing new procedures to minimise habitat loss. A policy of 'managed retreat' may be the best option, but with consequences that will include the loss of low-lying (fresh-water) habitat. All very depressing!
The next session moved closer to the birds, examining the effects of warming on coastal habitat and food supply: salt marsh plants (Gray), inter-tidal (Elliott & Hughes) and rocky shore (Kendall et al.) invertebrates, and breeding of coastal invertebrates (Lawrence & Soame). Some effects are relatively straightforward. Invertebrate communities may change, with cold water forms being replaced by more southerly taxa - provided of course that the latter are sufficiently mobile. Other changes may be more subtle. Estuarine species may be squeezed out. Some organisms produce differential sex ratios, depending upon ambient temperature: populations consisting entirely of lads (or girls) will not last long! Gamete growth may be inhibited by elevated temperatures.
Having laid the foundations (or, at least, exposed some of the problems and complexities) in terms of the physical and non-avian environment, the conference turned to birds. Humphrey Crick cheered up your correspondent with (British) predictions of increases in Little Egrets, breeding Spoonbills and an expansion in the range of Dartford Warblers, but tempered these with parallel losses of montane and northerly species. Many species are breeding earlier, although these effects may be stronger for small passerines than for more 'typical' coastal species such as waders and gulls. Tim Sparks followed this, with further evidence of change - both earlier arrivals and later departures, although again more related to passerines.
Studies of typically 'coastal' species followed. Red Knots breed close to the Arctic Ocean, with population-specific wintering grounds. Piersma suggested that, as the global temperature rises, summer sea ice and high Arctic tundra will gradually disappear, but this may not affect the Knot populations. Provided that the forests do not advance northwards faster than the tundra recedes, suitable habitat will remain. More likely are problems related to feeding sites for migrants: the loss of cockles from the Waddensee has been paralleled by a reduction in Knots. While this is perhaps due to over-exploitation by man, climatically induced losses of a similar nature could have the same consequences. Rehfisch & Austin; and Norris showed how climate changes within Britain already seem to be having an effect upon the local distribution of winter shore birds. Several species seem to be vacating the south west, and moving into the nutrient richer east, as the winter temperature becomes more acceptable. Norris highlighted the problems of disentangling distribution and abundance when analysing habitat change due to climate and/or land management. A more global perspective was provided by a review of the effects in the Antarctic. John Croxall showed how albatrosses, petrels and penguins are variously dependent upon ice floes, polynyas, upwellings, etc. for feeding or breeding sites. The relationships are often complex, and the problems are unlikely to be easily open to management or mitigation.
The final session examined some legal aspects of climate and the environment. Boere & Taylor reported that international legislation involves over 150 treaties and agreements, many of which are so bureaucratically inflexible. Few have been amended to the rapidly changing environment, but most are now linked to the UN Convention on Climate Change. They recognised that global warming may reduce the value of many existing reserves, and concluded that an integrated approach is essential, but many nations are reluctant (or unable) to put the wishes of the UN into practice. Two American speakers (Kentula and Zedler) reported upon the legalities of 'compensation' and 'restoration' following habitat damage or degradation. While directed more towards the protection of biodiversity in the face of 'development' than the effects of changing climate, the links were there: adverse effects can be compensated by careful forward planning. Clearly, research is needed to identify habitats that are most in need of protection, and to identify sites at which such protection could be introduced, in the face of a changing landscape. Atkinson et al. showed how this is beginning in Britain, describing their researches into the potential to restore inter-tidal, specifically salt marsh as a habitat for wintering Twites.
Overall, this was an important conference, covering a wide range of topics, including several (geomorphology, salt marsh plants, reproductive physiology of invertebrates) not normally included in bird meetings. Bill Sutherland drew the conference together with a spirited review, pointing out that the subject is not impossible – just difficult. Small scale studies of individual estuaries are more successful than larger analyses. Predictions of losses tend to be more accurate than of gains. The future is likely to be based upon interdisciplinary collaboration and co-operation. This conference certainly began by putting scientists from widely separate disciplines into a single room. The future will see whether this is successful.
For me, there were some disappointments. Humphrey Crick showed that some species have the potential to adapt to the climatic changes imposed upon them. Such evolution is based upon genetic variation in natural populations, and (as a geneticist) I found it very disappointing that the 'G' word was scarcely mentioned, and certainly never discussed. It may be that the environmental changes that we are witnessing may be too rapid for adaptation to be possible, but it has a place in such discussions. Another disappointment was the relative lack of people who actually study coastal birds. The BOU has got its programming right for the committed, but its marketing needs more thought. Maybe inviting junior researchers to speak is the way? Group leaders will support their protégés, but are less likely to pay for these protégés to listen to themselves. Bring in the youngsters (who are probably doing much of the work anyway), and you may double the attendance?
Finally, perhaps as a reward for all his hard work through the weekend, the BOU's Steve Dudley saw an Alpine Swift fly over the conference venue while packing the car after everyone else had left. Your correspondent (who 'needs' this species for Britain) heard the news with a mixture of tolerant understanding and irritation!