Are Habitat Fragmentation Effects Stronger in Marine Systems? A Review and Meta-analysis

The importance of habitat fragmentation in driving biodiversity loss has been recently debated. While the negative effects of habitat loss are well-documented, the effects of habitat fragmentation independent of habitat loss (e.g., habitat configuration) are more equivocal. Marine ecosystems have been underrepresented in past reviews, yet may differ fundamentally from terrestrial systems in their responses to habitat fragmentation because of the nature of energy/material flow, open population structure of most marine species, and narrow habitat extents. We conducted a systematic literature review and meta-analysis on the effects of habitat fragmentation in marine ecosystems. In our review of 180 studies from 28 articles, we found that habitat fragmentation effects were more often negative than positive, although the overall mean effect did not differ from zero. Interestingly, the mean effect was positive when the response was a measure of abundance, biodiversity, or population/ecosystem stability. Habitat fragmentation had overwhelmingly negative effects when it involved hydrological fragmentation. We found some support for the fragmentation threshold hypothesis via a weak negative relationship between habitat percent cover in the landscape and the habitat fragmentation effect. Results of this review on the effects of habitat fragmentation in marine ecosystems are largely consistent with another recent review finding that habitat fragmentation (independent of habitat loss) does not have consistent, negative impacts on biodiversity, and in many cases may increase biodiversity. Future work should focus on factors driving this variability and employ multi-scale frameworks to test for congruence between patch- and landscape-scale studies.