Biodiversity conservation in dynamic landscapes: trade-offs between number, connectivity and turnover of habitat patches
Abstract
1. Many species are adapted to landscapes with characteristic dynamics generated by ongoing habitat destruction and creation. Climate change and human land use, however, may change the dynamics of these landscapes. Studies have repeatedly shown that many species are not able to cope with such changes in landscape dynamics. Conservation policies must, therefore, explicitly address this threat. The way in which management should be modified when formerly static landscapes become dynamic or when landscape dynamics change is unclear. 2. Using an analytical formula for the rapid assessment of metapopulation lifetime in dynamic landscapes, we investigate if and how changes in one landscape attribute may be compensated by changes in another attribute to maintain species viability. We study such trade‐offs considering both spatial (number, connectivity of patches) and temporal (patch destruction and creation rates) landscape attributes. 3. We show that increasing patch destruction can be compensated to a certain extent by improvements in other spatial and/or temporal landscape attributes. Focusing on trade‐offs between management options reveals two key factors essential for management decisions: First, the trade‐offs are generally nonlinear irrespective of considering spatial or temporal landscape attributes. Secondly, species can be grouped according to their response to particular management options. 4. Synthesis and applications. We demonstrate the usefulness of an analytical formula for calculating trade‐offs between landscape attributes for a variety of landscapes and species. Two practical and robust management recommendations can be derived: (i) The nonlinearity of trade‐offs implies that the effectiveness of conservation measures depends explicitly on the current level of landscape attributes. It must, therefore, be taken into account in conservation decision making. In particular, the existing level of patch turnover is decisive: if it is already high, improvements in other landscape attributes are ineffective in maintaining species viability. Thus, monitoring the current level of landscape attributes is indispensable for effective biodiversity conservation. (ii) Compensation of increased patch destruction by increased patch creation is only suitable for species with high dispersal propensity adapted to variable environments (aside from habitat patch turnover). This implies that conservation policies which rely on such compensation, like offsetting and conservation banking, are feasible only for this type of species.
What the paper shows and why it matters
(AI-generated)
Many species live in landscapes where habitat patches are continually destroyed and created. Climate change and land use may alter this turnover, and how management should respond is unclear. For static landscapes, trade-offs between attributes such as patch number and connectivity are well discussed: they quantify how much of one attribute makes up for the loss of another. The paper notes that conservation planning software generally assumes constant exchange ratios between such attributes, and offsetting and conservation banking allow habitat to be destroyed if habitat is created elsewhere. For dynamic landscapes, such trade-offs are unclear, and simulations make a systematic exploration cumbersome. The paper takes on the assumption that one attribute can be traded for another at a fixed rate, whatever the state of the landscape.
The paper argues that, where habitat patches are continually destroyed and created, trade-offs between landscape attributes such as patch number, connectivity and destruction rate are generally nonlinear and depend on the type of species, so the effect of a conservation measure depends on the landscape’s current state, above all on how fast patches already turn over. It shows this with curves of equal metapopulation lifetime (the mean time until a network of local populations linked by dispersal dies out), calculated from an analytical formula for four example species types that combine low or high dispersal propensity with low or high exposure to environmental fluctuations. Higher connectivity makes up for increased patch destruction only for species with high dispersal propensity, and more patches only for species exposed to strong fluctuations. Creating patches to offset destruction is very effective only while destruction is still low and for species with both high dispersal propensity and strong exposure to fluctuations.
The paper reads these results as meaning that conservation measures cannot be ranked independently of the landscape’s state and the species type: strategies have to be attuned to each, and monitoring the current state of the landscape is indispensable. It concludes that offsetting and conservation banking suit only good dispersers adapted to variable environments, and only in landscapes with enough well-connected patches but still low turnover. It suggests that the nonlinear trade-offs could help to design differentiated trading rules and improve planning software. The results come from a formula and four example parameter sets, not field data.