PANTHER JUNCTION, Texas (AP) — Surrounded by large patches of straw-yellow sotol and withered prickly pear, federal botanist Joe Sirotnak summarized the causes of a massive plant die-off that has changed the Big Bend desert landscape, at least temporarily.
"This is from the freeze, and that's from the drought. It's a double-whammy," he said, with a sweep of the hand.
The first blow came when only 2.53 inches of rain fell during 2011 at the headquarters of Big Bend National Park, less than a fifth of normal precipitation. And the second was a five-day freeze in February 2011, when the mercury dropped almost to zero.
"The freeze and drought were acute events, unprecedented in living memory," Sirotnak said.
The drought extended throughout the Big Bend and into northern Mexico, and desert plants once thought to be nearly indestructible, such as creosote bush and lechuguilla — a spiky miniature agave known affectionately as "shin dagger" — succumbed in massive numbers.
The extraordinary plant mortality, first reported in the Big Bend Sentinel, extended to upland trees such as oak, madrone, piñon and juniper. And while this spring has been somewhat wetter, bringing flowers and some regeneration, the scars might last for years.
"The question that remains is, is this a long-term landscape-changing event or not?" asked Sirotnak, 41, who has worked at the national park since the late 1990s. "There's a good indication that 20 years from now, you could still see the effects of the drought of 2011 in the plant community."
Cactus specialist Michael Terry, a botanist at Sul Ross State University in Alpine, is seeing the fatal effects of the drought on these supremely hardy desert species.
"I'm just seeing them dying. I can think of a half-dozen species at least, maybe a dozen," he said.
"And here's the tricky part: These are the species that normally would have come up and produced seed by now that are not answering the call of spring. There is no water."
Terry's main worry is soil loss caused by the demise of vegetation such as creosote bush.
"Everything that would normally hold the soil in is now dead, and it will take years for the plants to come back. There will be this vulnerable period where horrible erosion can occur," he said.
Retired Sul Ross Professor Michael Powell, 74, who has studied the plants of the Big Bend for more than 50 years, said the biggest unknown is what the future holds.
"The million-dollar question is, will the flora change? No one really knows," he said. "I think what we're seeing is climate change, and it is expressed in these kinds of ways. It's been getting drier in West Texas for a long time."
So far in 2012, 2 inches of rain has fallen at Panther Junction, already below average this year but still wetter than in 2011. The ocotillo and surviving prickly pear are flowering.
And if the rains return to normal and keep coming, the effects of the drought of 2011 on the Chihuahuan Desert might fade, Powell said.
"If things stay that way long enough, for years and years, then ultimately the desert plants will come back," he said.
"But if we keep having these severe droughts without fairly long periods of normal precipitation, then it's logical we will see floristic changes in the desert."
Read more: http://www.mysanantonio.com/news/article/Drought-freezes-changing-landscape-in-Big-Bend-3519780.php#ixzz1tdFBkIQr
We did get .6 of an inch of rain last night from a passing thunderstorm.