The Effect of Incremental Reserve Design and Changing Reservation Goals on the Long‐Term Efficiency of Reserve Systems

Abstract

Selecting reserve areas based on percentages, such as 10% or 12% of a bioregion, is common in conservation planning despite widespread admission that such percentages are arbitrary and likely to be inadequate for the conservation of all biodiversity. Reserve systems based on these relatively low percentage targets are likely to require expansion in the future, resulting in the assembly of reserve systems over many years (incremental reserve design). How then will incremental reserve design, such as increasing percentage targets over time, affect the long-term efficiency of marine reserve systems? We used South Australia as a case study to investigate how changing percentage targets affects the contribution of individual planning units to efficient reserve design. Selection frequency counts provided a measure of a planning unit's conservation value. For the majority of planning units, changing targets led to a change in their conservation value indicating, for example, that planning units identified as high-value sites at a low-percentage conservation target may be of lesser importance when targets are increased. Despite the variability in the value of individual planning units at different targets, there was no loss in efficiency from incremental design of reserve systems based on systematic methods compared with purpose-built reserve systems (i.e., the system is assembled in a single iteration). The exception was when incrementally designed systems were based on South Australia's existing marine reserve system-a system developed in an ad hoc method. The result was reserve systems that were less efficient, less compact, and larger in size. This suggests that systematic approaches have an important role for efficient reserve design when there is uncertainty about the target level of reservation.

A systematic evaluation of the incremental protection of broad-scale habitats at Ningaloo Reef, Western Australia

“…Stewart et al (2007) have cautioned that there is a loss of efficiency when a reserve system that was not initially systematically designed is incrementally increased, and this may be evident at Ningaloo. However, if conservation targets are increased in response to changing goals, policy, threats or new information, this will probably be the case for the vast majority of older, existing marine protected areas implemented before systematic conservation planning methods became widely used.…”

Minimum data requirements for designing a set of marine protected areas, using commonly available abiotic and biotic datasets

“…Target scenario I set targets for all conservation features to 30%, as a mid-level estimate of the frequently recommended 20-50% in the scientific literature (Plan Development Team 1990;Dahlgren and Sobel 2000;Roberts et al 2003b;Parnell et al 2006;Stewart et al 2007). I used uniform percentage targets to give equal importance to all of the features.…”

Design of marine protected areas in a human-dominated seascape

“…However, this target is arbitrary and no general scientific agreement exists on what this threshold should be (Stewart et al 2007). Because of this lack of knowledge about which conservation targets should be selected to protect comprehensive and representative samples of biodiversity, we used a range of different targets.…”