Neighborhood habitat gains increase plant species richness in forest fragments

Kyle Rosenblad, Jon Sullivan

Theory and indirect evidence suggest that when new habitat is added to a habitat fragment’s local landscape, or “neighborhood”, species richness in the fragment will increase. Although this hypothesis is frequently assumed, it has not yet been tested directly with longitudinal data. In a natural forest regeneration experiment on Aotearoa New Zealand’s South Island, we use causal inference to show that 41-year changes in fragment-scale understory plant species richness are driven by changes in neighborhood habitat over the past century. This result supports theoretical predictions and highlights avenues for further research. Our findings can help inform prioritization of habitat restoration and conservation efforts.