Damage from Ike could affect coastal ecosystem of Texas for years

· Coastline of Texas under stress
· Higher sea levels from global warming adds to threat
· Texas coast crucial for a wide range of life

McClatchy newspapers, guardian.co.uk 22 Sep 08;

It was a violent dose of nature to a coast already hammered by decades of pollution, population growth and habitat loss. As scientists and land managers start to assess the storm's impacts on beaches, dunes and marshes, they are seeing signs of present damage and future worries.

"The impacts are going to be phenomenal," said Jim Sutherlin, superintendent of the Texas parks and wildlife department's 24,250-acre J.D. Murphree Wildlife Management Area, near Port Arthur. "We're going to take the critters that crawl or walk, and for the full stretch of the coastal zone that got the full impact of the coastal flood, they're just eliminated."

Although big storms are a natural part of any coastline's life story, the upper Gulf Coast of Texas was already under stress from many sources.

Coastal development and subsidence - a drop in the land's surface level as petroleum and groundwater are pumped out - have degraded large areas of marsh. Excessive organic material in coastal waters creates a "dead zone" of almost no oxygen in the upper Texas gulf.

And today's idea of a normal Texas coast could change dramatically in a future with higher sea levels from global warming. Earlier this month, scientists from three American universities concluded in the journal Science that a global sea level rise of 31.5 inches by the year 2100 should be the assumption. The highest conceivable rise, they estimate, is 6.5 feet.

Even the lower figure would put much of the existing Texas coastline permanently under water and would let a hurricane's strongest force reach farther inland. With coastal development, storms and rising seas all chewing away natural defences such as dunes and wetlands, damage from future hurricanes is likely to get worse.

"I'm sure what we'll see (from Ike) is more evidence of what happens when we don't maintain those natural barriers," said Larry McKinney, executive director of the Harte Research Institute for Gulf of Mexico studies at Texas A&M University-Corpus Christi.
"A hurricane is kind of a small-scale climate-change model," McKinney said. "We really need to start pulling together a long-term plan for responding to climate change."

The Texas coast is crucial to an astonishing range of life, from fish and amphibians to the birds that stop over during migrations along the great Central Flyway from South American winter habitats to arctic nesting grounds. What happens to the dunes, estuaries and marshes along the upper Gulf Coast can be felt across the entire hemisphere for years.

Under natural conditions, coastal ecosystems adapt to the effects of hurricanes and even use them to flush out marshes and estuaries, changing water chemistry and plant communities.

Storms can restart the cycles of succession, or the natural rhythm of birth, maturity, death and rebirth in an ecosystem.

Coastal habitats also absorb storms' energy, a lesson made real in 2005 when Hurricane Katrina rushed ashore unimpeded by the former marsh that once protected New Orleans. The long, narrow strips of sand that parallel the Texas coast and the marshes behind them attempt the same role; they aren't called barrier islands for nothing.

Ike's storm surge threatened to take out in a few hours the dune build-up of years, and to drown under seawater the marshes that survive on a mixture of fresh water and saltwater. The death of more marshes and the loss of the natural protection they provide is a certainty, experts said.

"These marshes were not in a healthy, dynamic state to start with because of human impacts," said Sutherlin, the wildlife area superintendent. Hundreds of acres, perhaps thousands, will be lost, he added.

"Everything's still under water," Sutherlin said. "It looks like an ocean out there."

The hurricane's effect on the complex natural system of the Texas coast will be apparent when scientists measure water quality in the gulf. The northernmost reaches of the Texas shoreline frequently becomes a "dead zone" with extremely low oxygen levels, but a hurricane quickly restores the oxygen, said Steve DiMarco of Texas A&M's department of oceanography.

Unlike the more widely publicised dead zone at the mouth of the Mississippi river, which is attributed to excessive nitrates from farming and other upriver sources, the Texas dead zone is linked to organic material of uncertain origin stirred up from coastal marshes. Sea level rise will complicate the problem.

"Over the long run, as the seawater flushes in, more organic material will get out," DiMarco said. But as to whether that will mean a bigger dead zone, "I won't go that far."

Steps for reducing hurricane threats range from restoring marshes to keeping people away from vulnerable areas. However, with each successive storm, each census showing coastal population increasing, and each new, higher projection of sea-level rise, Texas coastal experts fear that they have fewer choices.

"We have some options, but they're running out," said McKinney of the Harte Institute. "We need to take advantage of this disaster to learn."