An Ambassador for
Embattled Seagrasses Seeks
Global Monitoring System

The idea is to use remote sensing data already gathered each day by NASA satellites orbiting the Earth. The remote sensing imagery from a satellite itself is a form of spectral reflectance, though on a grand scale. Berlyn and Thorhaug use spectral reflectance at the individual plant scale. But whether done at the macro or micro level, both rely upon the same band of light waves and can be correlated, Thorhaug said.

Remote sensing has many advantages, including the ability to monitor seagrasses in extreme cold conditions or in hard-to-reach places. For example, if an oil spill blanketed a seagrass meadow in a remote part of the world, a satellite might quickly spot the signature of oil-stressed seagrass, potentially hastening a cleanup. More gradual impacts from other stresses could be measured over a period of months or years. Drawing upon satellite data from previous years, a nation also could determine where its seagrass meadows once flourished and restore them.

“It is a technology that works for all plant species. This is just perhaps the most dramatic application of it today,” said Philip Marshall ’02, an F&ES doctoral student and lecturer.

Thorhaug is president of the United States Association for the Club of Rome, which supports efforts to ensure a sustainable world, and is also president of the Greater Caribbean Energy and Environment Foundation. For decades she’s worked on seagrass restoration and protection projects for the United Nations. Noel Brown, former North American director of and now a special advisor to the United Nations Environment Programme, said Thorhaug is not only a highly respected scientist, but also a skilled communicator who works easily with people in other cultures around the world.

“I would call her equally a scientist and diplomat,” Brown said. In fact, if seagrasses have an ambassador, it is Thorhaug, who is knowledgeable about the condition of seagrass meadows in much of the world.”

The need for an aerial monitoring system is greatest among “poor developing countries, such as those in the Caribbean, that don’t have the skill sets and technologies to monitor their own resources,” Thorhaug said. “Along the shores of nations such as Nicaragua, Papua New Guinea, Indonesia and the Philippines are vast seagrass beds. But those nations generally have little money for environmental protection, especially for underwater plant species, regardless of their importance.” Unfortunately, “seagrasses are the last thing you preserve,” she said.

Signatures for seagrasses stressed by heated waters discharged from power plants and by low salinity already are documented and can be recognized in remote sensing imagery for areas off Florida, Texas and Jamaica.

While the technology is promising, it’s probably a decade away from worldwide implementation, Thorhaug said. There are about 50 seagrass species, and signatures for specific stresses vary among them, so the process of identifying signatures is time-consuming.

Even when all the signatures are documented, in places like the mouths of the Amazon, Mississippi and Nile rivers, where turbidity is a constant condition, the technology is unlikely to work, she said. Elsewhere, however, turbidity is usually temporary. Likewise, cloud cover is usually temporary. Thorhaug said aerial surveillance is worthwhile because it can precisely quantify degradation and pinpoint its causes.

At Yale, Thorhaug, Berlyn and Andrew Richardson ’98, Ph.D. ’03, determined just how sensitive seagrasses are to reduced salinity. They used spectral reflectance to study the effects of reduced salinity on an important seagrass species, turtle grass, Thalassia testudinum, usually the dominant vegetation in Atlantic subtropical and tropical underwater ecosystems. They found that Thalassia is unable to endure salinities that drop to 16 or 20 parts salt per thousand parts water for periods of 48 hours or more—levels that seagrasses are often subjected to when freshwater flows are concentrated in one area. “They get sick and die, in short,” Berlyn said.

Thorhaug remains positive.

“You have to be an optimist if you are going to find good solutions,” she said. “You have to keep working. You have to believe there is a better way. People call me a technological optimist. That is what I am.”

Email This Article           Print This Article

Top of Page | Fall 2009 | environment:YALE