CAPE TOWN, Nov 28 (Reuters) - A global satellite system should come on line next decade, potentially saving billions of dollars and thousands of lives by boosting preparedness for natural disasters, a top scientist said on Wednesday.

Monitoring changes in climate, the Global Earth Observation System of Systems (GEOSS) should also help health officials prevent epidemics and guard against man-made environmental damage, said Jose Achache, head of the group behind the project. "I'm an optimistic guy. So, I think in ten years from now we'll have a fully operational and fairly complete GEOSS," Achache, director of the Geneva-based intergovernmental Group on Earth Observations, told Reuters.

He spoke as ministers and officials from 70 countries assessed progress on the Internet-like monitoring system, which links ocean buoys and satellites to reduce vulnerability to disasters and environmental change.

He said technology had already significantly reduced death tolls from disasters, and GEOSS would take that further.

"We've come a long way. The best example we can give today is this tragic hurricane in Bangladesh two weeks ago, where we had to count the victims by thousands," he said.

"But, if you think about it, 15 years ago the same hurricane killed 140,000 people and 15 years before the number was 500,000."

Achache said the fewer deaths from Hurricane Sidr was directly due to better preparedness, heightened global observation and sharper modelling, which allowed authorities to track the hurricane and better forecast its intensity.

He said GEOSS could also help authorities control outbreaks of contagious diseases like cholera and meningitis by monitoring environmental conditions where they occured.

It will be able to gauge human environmental impact amid global concerns of accelerating climate change, such as that potentially caused by an Indian proposal to divert river flows to irrigate arid land, he said.

But Achache said a "huge task" remained ensuring the complex GEOSS system, officially only two years old, will work. Securing funding remained a challenge as well, he said.

"I guess we'll have to demonstrate (that) it's useful, that it is providing benefits to society," he said. (Reporting by Wendell Roelf; Editing by Michael Winfrey)

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