The forests of Hawaii

I have spent the last few days visiting the forests of the Big Island of Hawaii, hosted by Greg Asner. We are looking to bring the long-term ecosystem studies going on here into the fold of our global ecosystems monitoring project, GEM. As well as being fascinating in themselves, Hawaii's forests bring lots of advantages as this is where much of our understanding has been developed on how nutrient cycling changes with ecosystem development. The substrate is all volcanic lava, with forests growing on lava soils ranging from a few hundred years to hundreds of thousands of years.

The other astonishing thing about Hawaii is the lesson it provides in invasion ecology. The native plant and animal species of Hawaii are descendants of the few that made it across the vast stretches of the Pacific by wind, ocean currents or animal transport. There they have evolved, diversified and radiated into many unique species that are found only in Hawaii. The absolute levels of diversity are low compared to, say, Amazonia, but the levels of endemism (species found here and nowhere else) are extremely high.

Since humans arrived about a millennium ago, and particularly in the last century, they have been bringing in outside species and rapid rates, whether by accident or design. Many of these species are invading and altering native ecosystems. One extreme example is strawberry guava Psidium cattleianum,  native to the Atlantic rainforests of Brazil. In Hawaii it forms incredible dense thickets that suppress other vegetation, and an advancing front that is gradually marching through the forests.  Hawaii is in the front line of understanding ecological invasion and how to stop it.