This long-term experiment measured the difference in colonization and extinction rates of connected habitat fragments versus isolated fragments. The connected fragments were linked by a narrow (150m by 25m) strip of habitat. These habitat corridors increased the biodiversity of connected fragments by 14% after 18 years compared to their isolated counterparts.
In a large and well-replicated habitat fragmentation experiment, we find that annual colonization rates for 239 plant species in connected fragments are 5% higher and annual extinction rates 2% lower than in unconnected fragments. This has resulted in a steady, non-asymptotic increase in diversity, with nearly 14% more species in connected fragments after almost two decades. Our results show that the full biodiversity value of connectivity is much greater than previously estimated, cannot be effectively evaluated at short time scales, and can be maximized by connecting habitat sooner rather than later [Damschen 2019: 1479].
The authors note that 70% of the world’s forest area is within 1 km of an edge – meaning Earth’s forests are very fragmented. They stress that connecting habitat fragments is critical to the success of habitat and biodiversity conservation.
Conservation plans that ignore connectivity, such as plans that focus solely on habitat area, will leave unrealized the substantial, complementary, and persistent gains in biodiversity attributable specifically to landscape connectivity [Damschen 2019: 1480].
Damschen, Ellen I., et al., 2019, Ongoing accumulation of plant diversity through habitat connectivity in an 18-year experiment, Science 365, https://science.sciencemag.org/content/365/6460/1478.abstract.