The struggle to save Earth's largest life form
(Page 2 of 2)
But there may be limits to how broadly these results apply, others say. Even without pressure from climate change, reefs also face pressure from overfishing, farm and ranch runoff, and soil erosion.Skip to next paragraph
Subscribe Today to the Monitor
Last July, after several years of debate and negotiation, Australia's federal government took a significant step by declaring fully one-third of the reef a no-take zone - no fishing, capturing live fish, or collecting corals. Previously, no-take areas covered only about 5 percent of the reef.
At the same time, the state of Queensland adopted a program for reducing the silt and nutrients that flow onto the reef from rivers in the region. The silt can cut light and smother young coral before they can replenish a bleached area. The nutrients can lead to explosions of algae and Crown of Thorns starfish, which can turn healthy reefs into drab undersea barrens.
Having figured out the historical impact of silt from rivers (see story, below), an AIMS team is embarking on a five-year project to pin down more precisely the biological effects of the nutrients and soil across broader reaches of the reef system.
As these scientists head to the reef to get a better handle on the factors that determine the GBR's resilience, others are using those data to build models to forecast resilience.
For example, Scott Wooldridge is developing a "state of the reef" computer model at AIMS that will allow conservation managers to rank the resilience potential for different reefs or reef segments. The model has the potential for use worldwide. So far, he's included three elements: adequate levels of grazing fish on the reef to keep algae at bay, water quality, and increased heat- tolerance among coral - which he acknowledges is the weakest link in the chain in terms of biological research.
The model points to some disturbing results. Australia - and specifically, the Great Barrier Reef Marine Park Authority - may have chosen the wrong approach when it set up its no-take areas, he says.
His preliminary results suggest that the northern third of the reef probably should get the most conservation attention. The park agency, by contrast, set aside ecologically representative areas scattered throughout the reef. That made sense at the time, Dr. Wooldridge says, given what scientists then knew. But the northern segment is more pristine and faces fewer stresses because fewer people live and visit there. While it will likely feel the bleaching effects of climate change more strongly at first than reef sections farther south, it still stands a good chance of surviving. Thus it will be able to provide the larvae that will ride prevailing currents south to reseed portions of the reef that are under greater multiple stresses.
It's a controversial notion, Wooldridge acknowledges, and calls into question the strategy over which the government spent so much time and political capital.
"With proper management, you can still have a viable reef by 2050," he says. "But the implications are that we need to conserve more in the north."
To persuade people to protect the environment, scientists' future projections can fall short. Often they need to tease out clues from the past.
As Queensland was debating whether to protect the Great Barrier Reef by restricting river runoff, coral researchers could point to historical records - not to mention contemporary recollections - that the state's rivers had grown more silt-filled since European settlement, threatening the reef. But they had very little data to back it up. "We knew things were happening," says Malcolm McCulloch, a geochemist here at Australia National University. "But we didn't know the true scale of what went out to the reef."
In what many here see as a seminal piece of sleuthing, Dr. McCulloch and colleagues from the Australian Institute of Marine Science took core samples of coral, which develop annual growth bands like trees. Looking for chemical signatures of soil run-off, particularly the element barium, they found that from 1750 to about 1870, sediments from the Burdekin River - the country's second largest when it floods - reached the inner portions of the reef "only occasionally." After about 1870, the amount of soil disgorged to the inner reef grew five- to 10-fold as land upriver was cleared for ranching and grazing began.
Queensland passed runoff regulations last year.