May 22 is International Day for Biological Diversity—and this year, the focus is on island biodiversity. Since most of our project sites are located on islands, we thought we’d celebrate this holiday with a deeper dive into what makes life on these places so interesting.
Isolated from their mainland counterparts, island plants and animals evolve independently. Since no genetic mixing occurs with populations in other places, new species unique to the island form over time. This high rate of speciation, or creation of new species, makes islands important drivers of biodiversity. Islands have higher concentrations of endemic species (animals and plants found nowhere else) than continents, and the proportion of endemics increases with an island’s degree of isolation, size, and topographical diversity (which leads to different habitats).
Why is biodiversity important? Madhavi Colton, CORAL’s program director for the Reefs Tomorrow Initiative, says biodiversity makes ecosystems more stable. She offers the example of coral reefs in the Caribbean, which used to have many different species of herbivorous fishes. “Overfishing reduced the abundance and diversity of herbivorous fishes leaving urchins as the only species keeping algae in check,” she explains. “When a disease wiped out the urchins, there were no more herbivores left to take their place and algae overgrew the reefs.” When there is a dip in the abundance of a key type of animal in a diverse ecosystem, the consequences will be “less dire because there are other species that play similar roles to pick up the slack,” says Madhavi. Read more about coral reef biodiversity here.