Work Package 4: Harvesting strategies in a spatially structured environment

Leader: Ivar Herfindal, NTNU

Environmental changes introduce new challenges for the implementation of multispecies harvest strategies, as they force temporal and spatial shifts on species distributions and interactions (WP3). Our aim in this WP is to develop stochastic models for how choice of multispecies harvest strategies will affect the dynamics of interacting species in space and time in a changing climate.

In practice, one tends to harvest more where one expects to find large population densities. Harvesting strategies that have been previously examined do not take this spatial aspect into account (50, 51). Our modeling approach will provide a two-species extension of the model of Lande et al. (52), who analyzed the effects of local density regulation, dispersal, and spatially correlated noise on the spatial scaling and stochastic fluctuations of population density of a single species.

This linearized model may be generalized to describe the interaction between two species, where the noise acting on the two species can be spatially correlated. This model may describe a competition system or predator-prey dynamics according to the signs of the parameters expressing the  different types of regulation and can be used to derive how harvest affects the spatial scale of correlations in population densities within and between species. In particular, we will investigate to which extent spatially explicit harvest strategies have any advantages compared to the simple, non-spatial proportional harvesting.