Current warming and likely future impacts - Climate Change: Biological and Human Aspects - page 293

pond can have the effect of increasing plant diversity on the surrounding land. As has
been shown in a Florida reserve, fish can reduce, through predation, the abundance of
dragonfly larvae (such as Anax junius and Erythemis simplicicollis ) in ponds, which
leads to fewer adult dragonflies in the air that would in turn prey upon pollinator
insects. Fewer predating adult dragonflies means more pollinator insects and so more
plants pollinated, hence, in theory, more plants (Knight et al., 2005). So not only does
conservation management need to be conducted with regard to the landscape level to
facilitate migration between sites, it also needs to be done at the ecosystem level, not
just for the ecosystem but to enable trophic cascades between ecosystems to realise
biodiversity synergies.
With climate change, managers of such sites will need to consider a number of
parameters to their local conservation strategy. The first is 'ecosystem resilience'.
This can be defined as the ability of an ecological system to absorb disturbances
while retaining the same basic structure and ways of functioning, and to have the
capacity for self-organisation and the capacity to adapt to stress and change. This
definition differs from another ecological definition of the same term as being the
speed with which a community returns to its former state after it has been disturbed.
With current climate change, globally the IPCC anticipate a long-term warming
trend and so in this light absorbing disturbance is more appropriate than returning to
a former state. Having said that, global climate change is one thing, but local vagaries
of weather and climate are another. Here the ability to return to a former state is
of value.
The importance of these two views of ecosystem resilience is highlighted by under-
standing the manner of species' range shift with climate change. In 2011 ecologists
Regan Early and Dov Sax highlighted this when looking at 15 amphibian species
in the western USA, making the following predictions. First, interdecadal variability
in climate change can prevent range shifts by causing gaps in climate paths, even
in the absence of geographic barriers. Second, the somewhat unappreciated trait of
persistence during unfavourable climatic conditions is critical to species' range shifts:
a key predictor of success was a species' ability to live with unfavourable climate
for - in the case of their amphibian study - up to a decade. Third, climatic fluctu-
ations and low persistence could lead to endangerment even if the future potential
range size is large. These considerations may render habitat corridors ineffectual for
some species, and conservationists may need to consider managed relocation (species
translocation).
Ecosystem resilience should not be confused with ecological resistance, the ability
of a community to avoid displacement from its present state by a disturbance. What
ecological conservationists need to consider is how to build in ecosystem resilience
so as to manage ecological resistance because we do expect communities to migrate
with long-term climate change. This problem of terminology is common in science,
not to mention other walks of life. (Earlier there was the example of the misleading
term medieval climatic optimum and we shall in the coming chapters see others, such
as population 'fertility', climate 'tipping point' and low 'carbon' economy.) While
it is difficult if not impossible to impose vocabulary (living languages are dynamic),
we can and need to be clear about what we mean.