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Fossil Record Aids Ecosystem Reconstruction


In a remote spot on the Hawaiian Island of Kauai, in a large collapsed cave, a scientist with the National Tropical Botanical Garden its tracing its ecological history and working to reconstruct the ancient landscape.

David Burney studies ancient environments, and the fossil pits at Mahaulepu are his workshop. One of his projects for the National Tropical Botanical Garden is to explore this grotto. "I call this place a poor man's time machine," he says. "You've got the rock itself almost one-half million years old. You've got the cave, which formed sometime in the last few hundred thousand years. You got stalactites and stalagmites, like this really huge one over here. You know, this [stalagmite] probably formed over a period of some tens of thousands of years, and then all the sediment inside [the cave] -- which is the part that we like the most -- was deposited over the last 10,000 years."

The cave collapsed 7,000 years ago when the sea level rose, and now, David Burney is excavating the sinkhole, layer by layer. Close to the surface, he uncovers present day relics like Polaroid film backs and Styrofoam cups. Deeper still he finds iron nails, fishhooks and hemp sailcloth from 18th century European ships. Then, artifacts from early Hawaiian life -- before European contact -- emerge from the muck.

"Here is a 500 year old yam that we found in here to give you an idea of just how wonderful the preservation is," he says. "We find gourds with designs on them and wooden and bamboo artifacts (like) pieces of canoes. We found canoe paddles and adze handles."

Using a process he describes as a cross between oil drilling and open pit mining, David Burney and his helpers have found fossils of giant flightless ducks and geese, and bird-catching owls, as well as the remains of plants, seeds, pollen and leaves that date back 10,000 years.

"We pump the water out so I can dig in dry conditions, and as I dig down I find these flooded grottos up under the walls and we dig back into the walls there," he says. "That's where we find the best stuff because a lot of things float up in there, and when they are deposited they don't come back out. This is the largest of our pits. This is the type location for at least 7 extinct birds that haven't been found anywhere else."

David Burney takes a bucket of silt from the sinkhole and begins to filter it through thin wire mesh screens. "This is called wet screening," he explains. "Since the mud is already wet, the best way to get the fossils and artifacts out is to wash them through a nesting set of screens. We get the big stuff on the top screen and the little stuff on the bottom screen. And then pick out the remainders."

What he comes up with is a claw from an extinct land crab that he thinks people probably ate. "One of the most interesting things about the archeology here is the richness of dietary items," he says, adding that the pit served as a garbage dump. "And so when we look through the layers from early Hawaiian time to European time and beyond, what we see is at least 16 different kinds of shells, which were dietary items and over time there was probably a resource crunch… as there were more and more people, the shells tend to get smaller. This seems to suggest that these people were [like people everywhere]. They had to have something to eat and as they got more numerous many of their food resources were overtaxed.

David Burney is seeking answers to some big questions: When did the first humans come to this island? What was it like they arrived? And, how has the ecosystem changed? The fossil record tells that story and he is using it as a guide to reconstruct the landscape.

For example, he has transplanted a species of palm from a nearby island that fossils indicate once grew on Kauai. "This is the fruit of the lolu palm," he says. "We planted these here, and they are thriving. The point is that a lot of the plants that are growing here were represented as fossils and appear to be common here before and are very rare today and they grew in a much wider array of habitats than they do today, including down here in these dry coastal areas."

David Burney says the fossil record at Mahaulepu demonstrates how an ecosystem responds to human impact and natural events over time. He says we can learn from it how to better protect the world we live in today.

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