Today, May 22, is International Day of Biological Diversity and the theme for this year is ‘Island Biodiversity’. Chosen to coincide with the designation by the United Nations General Assembly of 2014 as the International Year of Small Island Developing States, the theme also acknowledges the recent decision by the Convention on Biological Diversity, “to strengthen the implementation of the Programme of Work on Island Biodiversity”
I am never very convinced by the concept of “International Day of” – does it really work to raise consciousness of the issue or is it just a sop to a subject that you cheerfully ignore for the rest of the year? (but I am a curmudgeon and hate Valentine’s Day, Mother’s Day and the ridiculous forced jollity of New Year’s Eve to name but a few!). However, there must be some merit in it as the numbers of ‘International Days’ do not seem to be decreasing…
Islands can have unique fauna and it was the study of the differences in island species by Charles Darwin and Alfred Russel Wallace that helped develop the theory of evolution. In more recent times islands have become very important as refugia for species under threat such as the Seychelles magpie-robin, Copsychus sechellarum or the kakapo, Strigops habroptilus. But islands are also particularly vulnerable; to invasive species, or catastrophic climatic events. The small island states are some of the most active proponents of global action on climate change because they are already suffering from the impacts.
Thus the idea of a special day to raise awareness of the glories and threats of island biodiversity is both interesting and important; but what has this got to do with the Woodland Trust?
Island biogeography has become an important area of study within natural sciences attempting to identify the factors that affect the species richness of isolated natural communities. The theory was developed to explain species richness of actual islands but it became obvious that you could apply the same analytical techniques to other types of “island” such as a lake surrounded by dry land, a fragmented patch of rainforest, or any semi – natural habitat surrounded by human-altered landscapes. Island biogeography theory can be applied to any ecosystem surrounded by unlike ecosystems.
Patch dynamics, metapopulations and gene flow all work together to add complexity to a simple equation, if an island of suitable habitat is surrounded by a sea of unsuitable habitat – ancient woodland surrounded by intensively managed farmland – the species on the island will become isolated and more vulnerable to events both natural and human induced. If we are serious about wanting to protect our ancient woods for the future we have to look at more than just managing the wood itself, we have to consider the resilience of the landscape as a whole.
In this instance, we are discussing ecological resilience rather than this being an economic issue. Resilience is taken as the capacity of an ecosystem to respond to disturbance by resisting damage and recovering quickly. Profound changes can occur to ecosystems when the magnitude or duration of disturbance is sufficient to push it over a tipping point, beyond which recovery is no longer possible. There is an imperative for increasing the resilience of and landscape arises from a drift towards structural, functional and taxonomic homogenisation, and to pests and disease threats and climate change.
Broadly, diverse landscape systems with mixed species and structure are likely to be more resilient than limited species mixes and with low structural diversity. ‘Functional connectivity’ is a property of both the quality of the matrix between habitat patches and of the species being considered. It is not necessary for habitats to physically link in order to promote gene flow.
Maintaining and developing resilient landscapes requires consideration of all semi-natural habitats and associated species. The need to develop resilient landscapes is more than just undertaking landscape scale activities for an individual species or habitat and may require new levels of analysis in biodiversity policy and delivery.
Frances Winder, Conservation Policy Lead