Teraina was our last destination, the last island in our expedition. Teraina is small, 3.5 miles long by 2 miles wide, and it has a human population of 900. Located between Palmyra and Tabueran, it is probably the most difficult island in the northern Line Islands to get to. With no scientific data available on its coral reefs and no diving reported, the most we knew about it was just hearsay. However, we read that Teraina, also called Washington Island, has a 2 km freshwater lake and a pristine forest of Pisonia, a native tree that is in decline throughout the central Pacific. We were told not to go because of its treacherous currents, rough seas and huge breaking waves. We were told not to go because there is no anchorage anywhere around the island. We were told not to go because it is extremely difficult to land on it, and because even local boats capsize on the surf while trying to get to and from the island. So with all this important advice we went anyway.
What we found in Teraina surprised us enormously. Because of the small human population size and the typically rough seas around it we expected to find all of the above. But we found none, except the lake.
The lake is large and surrounded by an impressive jungle of coconut trees. The surface of the lake is about one meter above sea level, and this level is maintained by a man-made dike. In years with abundant rainfall (usually around 2 meters per year) the lake overflows and a small stream flows into the sea. In drier years, the water is retained. The lake is about 10m depth in its center. The shallow bottom of the lake is covered by fossil shells and corals, and logs and coconuts which are decomposing slowly. The introduced Tilapia fish, a basic food staple in other parts of the world but not appreciated in Teraina, is abundant. At about three meters down there is a false bottom separating two distinct bodies of water. Above there is a layer of brownish water; below there is a green layer.
The green layer is a green soup in the bottom of the lake, made of triturated plant material, planktonic algae and bacteria. This green interface appears solid but you can dive straight through it. Diving here is phantasmagoric.
We dived on the fore reef of Teraina and found no sharks or snappers, which were the most abundant predators elsewhere. Most fishes were smaller than a foot. We dived on a large coral terrace northwest of the island, and found virtually no living coral, but a carpet of green seaweed four inches thick.
Alex Wegmann, a botanist of the Fish and Wildlife Service conducting research on the forests in Palmyra Atoll, joined us for the trip to Teraina to survey the remnant Pisonia forests. However, there were no forests remaining, only small patches with a few large trees. That came as a shock to him. He was also surprised because "I saw only one species of land crab when there should be five species here, including coconut crabs." In addition, we saw relatively few birds.
Why is Teraina so different from the other islands in the archipelago? Kiritimati and Tabuaeran are heavily fished, but still have some corals and some sharks, and no green seaweed monocultures. The answer is that 900 people is too many people for such a small island; too many people per hectare of reef.
Pisonia trees were cut and replaced with coconut trees for the copra; crabs have been eaten; and, as we learned from some local fishermen, sharks, turtles and even melonhead whales are hunted for local consumption. Moreover, the lake might be pumping water rich in nutrients into the reef. Aware of this possibility, Forest Rohwer and his team collected water samples from the lake, a well, and on the outer reef. Back in San Diego, they will analyze the samples and determine whether the lake is polluting the reefs and turning them into a green field.
We visited Teraina and its lake; we talked to its hospitable people; we ate the Pandanus fruit; we dived in its reefs. We solved one mystery, and we have a few more to solve now.
A final anecdote comes to my mind. We drove around the island in one of four small trucks, led by the police chief. We stopped on the southwest part of Teraina, in the middle of the largest Pisonia patch, near an immaculate beach washed by shifting blue waves. There was no trash on the ground. The sunlight was filtered by the large leaves, dying everything inside the forest with a deliciously light green light. It was like being on an island inside an island. I told him that that place was beautiful. Surprised and apparently annoyed, he asked me why I thought that was beautiful. In his opinion, that place was a mess. Can we agree on common goals for preserving our rich natural heritage when our values can be so different?
Scripps Line Islands Expedition 05