Translocaties in natuurbeheer: controversieel en essentieel

Habitat loss and fragmentation of (semi)natural habitat are the most
important drivers of ongoing biodiversity loss. Nevertheless nature ma-
nagement generally focuses only on the regulation of abiotic and biotic
processes within habitats. Dispersal between habitats is often neglected,
despite its pivotal role in conservation. Here I show that in a meta-po-
pulation context colonisation is required to counter the local extinction
in habitat patches. The equilibrium between colonisation and extinction
defines the patch occupancy, that is the fraction of the patches occupied
by a species, and both processes. I continue by showing that both proces-
ses (extinction/colonisation) are heavily influenced by the size of the local
populations and the distance between patches. Clearly size and connec-
tivity trade-off: while large areas and populations do not rely so much on
connections with other habitat, because extinction risks are relatively low,
small areas and populations need to be well connected to allow for colo-
nisation. In our fragmented landscapes with small and isolated habitat
patches, this is clearly a bottleneck. Finally I discuss the different options
we have to increase dispersal in such fragmented landscapes. Creating
larger habitat and stepping stones between habitat are obviously the only
sustainable options in the long run, but require a strong policy towards
conservation, including clear land-use choices. Anthropogenic dispersal
(translocation of organisms) on the other hand might be required in the
short term to maintain healthy communities and (meta)populations. I
conclude by noting that translocation will not be sufficient to conserve
ecosystems, but it could be an effective measure that buys us time while
we search for sustainable solutions for the biodiversity crisis we are facing.