Today’s LA Times has a distressing take on the damage the Sawtooth fires wrought on the Mojave Desert’s populations of juniper, piñon and Joshua trees, and raises questions as to whether the fires are a preview of coming attractions in a climate-changed world, or a rare event caused by the especially rainy conditions in the desert winter before last combined with the especially hot conditions earlier this summer.
Scientists do agree that it will take centuries, if not millenniums, for the desert to recover.
“It won’t be on a timeline we humans would like, but it will happen,” said Tasha LaDoux, Joshua Tree National Park’s botanist.
Inside the park, new growth provides fodder for the debate over whether the fragile, arid landscape is undergoing dramatic change.
At the scene of a 1995 fire, not a single juniper or piñon pine seedling has come up after 11 years. But healthy, 3-foot “pups” have sprouted from the roots of once seemingly dead Joshua trees. The pups may or may not survive, scientists say, because in drought years they may be gnawed by thirsty rodents and ground squirrels. Meanwhile, native apricot mallow, bright-green cheesebush and golden California marigold are blooming even in August.
Along a sandy road in the western section, the scene of a 1999 blaze that scorched 14,000 acres, a beige sea of grasses spreads beneath burned Joshua trees bleached silver by sun and rain. The new growth consists of native bunch grasses and a pair of noxious, ankle-scratching weeds.
These two nonnatives, known as red brome and cheatgrass, form highly flammable carpets between native shrubs and trees, and many scientists believe they are the main culprits behind increasing fires.
“These invasive grasses fill in the spaces between the desert plants. They carry the flame through at a very high rate, and much hotter. It spreads a lot faster,” Sall said.
Native to Mediterranean Europe and Asia, the weeds were probably blown across the West by the wind, tracked in by hikers’ boots and construction equipment, and excreted by livestock. Researchers at UCLA and elsewhere say the weeds appear to capture nitrogen from smog-laden air more readily than native plants, eventually choking them out.
The whole story is worth reading. Disagreement is rife among the desert ecologists the Times interviewed.
Meanwhile, while the California deserts become more flammable, the ocean is getting noisier, according to a UC San Diego Scripps Institution of Oceanography study cited in Science Blog:
Mark McDonald of WhaleAcoustics in Bellvue, Colo., and John Hildebrand and Sean Wiggins of Scripps Oceanography accessed acoustic data recorded in 1964-1966 through declassified U.S. Navy documents and compared them against acoustic recordings made in 2003-2004 in the same area off San Nicolas Island, one of the Channel Islands more than 160 miles west of San Diego.
The results showed that noise levels in 2003-2004 were 10 to 12 decibels higher than in 1964-1966, an average noise increase rate of three decibels per decade. The culprit behind the increase, according to Hildebrand, appears to be a byproduct of the vast increase in the global shipping trade, the number of ships plying the world’s oceans and the higher speeds and propulsion power for individual ships. The noise detected off Southern California originates from ships traveling across the entire North Pacific Ocean. According to Lloyd’s Register figures quoted in the JASA paper, the world’s commercial fleet more than doubled in the past 38 years, from 41,865 in 1965 to 89,899 in 2003.
“We’ve demonstrated that the ocean is a lot noisier now than it was 40 years ago. The noise is more powerful by a factor of 10,” said Hildebrand, a professor of oceanography in the Marine Physical Laboratory at Scripps. “If we’ve doubled the number of ships and we’ve documented 10 times more noise, then the noise increase is due to both more ships and noisier individual ships than in the ’60s. And that may be because the ships are now bigger, faster and have more propulsion power. The next step is to understand what aspect of modern shipping has resulted in more noise per ship,” said Hildebrand.
Is there an impact on marine life? The scientists don’t know, but it seems to this non-scientist that it could have a profound impact. The suggestion that the noise impact of ships be regulated, and/or that shipping lanes be re-routed, will likely soon appear on the environmental global policy agenda.