Under climate change, reserves are likely to become increasingly unsuitable for the species they were designed to protect. For freshwater ecosystems, which are often overlooked when planning for connectivity in favor of terrestrial or marine ecosystems, climate change may alter flow, depth, or even the existence of waterways that support high levels of biodiversity. Reserve planning can take either a proactive route (protect and connect areas that include future species distributions) or a reactive route (add new reserves once the distribution of species shifts beyond the borders of existing protected areas). Bush et al., in their forthcoming publication in Journal of Applied Ecology, systematically compare these two approaches to determine their efficiency in the long-term. They focus on odonates (dragonflies and damselflies) in eastern Australia, as a group that’s both highly endemic the region and mobile, and so may benefit from additional protected space outside of just freshwater habitat. In addition to evaluating the reserve design process, they also look at whether connectivity is effective when only connecting river channels longitudinally versus including neighboring sub-catchments in reserve plans as well.
With clear and straight-forward results, they conclusively demonstrate that using a proactive approach (i.e. including predicted species distributions in reserve design) is much more efficient for preserving freshwater biodiversity. Reactive planning meant species were 16% less likely to be protected by 2055 and 30% less likely by 2085. Despite its higher cost in the short-term, proactive planning becomes more efficient in the long-term because fewer existing reserves become unsuitable in the future and it requires fewer additional areas to meet gaps in protection in the future. In addition, the authors showed that conservation planning was less effective when considering only longitudinal connectivity for freshwater systems. By connecting neighboring sub-catchments, in particular headwaters at higher elevations, mobile species will be able to expand their range more easily through the use of all available corridors.
