Habitat loss does not affect ecological connectivity for a habitat engineer with short dispersal

Abstract

Habitat loss, directly linked to anthropogenic activities, is a key driver of biodiversity loss globally; in combination with habitat fragmentation, it leads to smaller, more isolated population patches. Such changes in habitat configuration can negatively impact population connectivity (i.e., the supply of individuals locally or from neighboring patches) and compromise metapopulation persistence. For short‐distance dispersers, loss of connectivity between habitat patches may have a smaller impact on persistence than reduction in patch size. We investigated the relationship of habitat loss and associated changes in habitat configuration with demographic connectivity using a temperate marine system of laminarian kelps as a case study. Kelps are an important ecosystem engineer, currently experiencing global declines because of habitat loss. We ran two in silico experiments of habitat loss by removing habitat in 10% increments from 10% to 90%, and 1% increments from 95% to 99%: (1) suitable habitat was removed randomly; and (2) the probability of habitat loss was inversely proportional to patch size, with smaller patches having a greater likelihood of loss. Kelp habitat was clustered into patches based on spatial dependencies derived from Lagrangian particle tracking simulations. We found that area‐weighted habitat loss created a trade‐off between structural and functional habitat fragmentation. While this form of habitat loss resulted in fewer, larger patches (less structural fragmentation) than random loss, patches were more isolated, and consequently, the metapopulation showed lower betweenness centrality and modularity (more functional fragmentation). However, under both random and area‐weighted loss, patches were supported by self‐replenishment for 90% of recruited individuals, receiving minimal inflow from neighboring populations. These results suggest that although rescue potential of patches from neighbors is low, especially in the case of area‐weighted loss, the demise of individual patches may not trigger the loss of neighboring ones. Thus, the probability of metapopulation persistence remains high, given only a few patches need to remain. We showed that some but not all theoretically predicted relationships between habitat configuration and metapopulation dynamics are supported in real‐world ecological systems.