Different species occupy different niches in the web of life. Knowing what species inhabit an ecosystem, and how many of each kind there are, is critical to understanding that ecosystem's structure and function, and predicting future changes. Scientists who look at the variation of life in a forest, a stream or a patch of soil are looking at its biodiversity.

When scientists assess an area’s biodiversity, they look at species richness (how many different species there are) and relative abundance (the number of organisms each species has). A healthy ecosystem is a balanced one—with enough predators, prey, producers and decomposers to keep the food web stable. When the system is thrown off balance, that web can quickly unravel. Forests may struggle to grow when the deer population explodes, or fish near the top of the food chain may suffer when tiny organisms at the base disappear. But when biodiversity levels are right, it can strengthen the ecosystem to better resist stresses like climate change and invasive species.

Biologists at SERC look at biodiversity all across the coastal zone. Some of the species they track, like blue crabs, are already known and loved. Others have made their mark as invasive species. They survey aquatic creatures in the water, and make censuses of trees in the forest. Some of their long-term surveys have been going on since the 1980s. They also investigate what can impact biodiversity—threats such as pollution and climate change—and how biodiversity can strengthen human society as well as the environment.