California’s Redwoods are Suffering from Fog Decline
Image Source: Flickr. By: Airstream.
Have you ever walked out your front door one morning, only to encounter a thick, white fog? Perhaps you’ve driven down a highway or country road at night and straight into a fog bank? These low-lying clouds may seem like a nuisance to some. Others may see them as a great photo opportunity. And for others, particularly those out at sea, fog can sometimes be the difference between life and death.
People are not the only ones affected by fog. In fact, the lack of fog in California is having a major negative effect on the health of the mighty Redwood trees. New research suggests that over the past 100 years, the average daily fog in California has decreased by more than 3 hours, causing Coast Redwoods to lose more water in the dry summer season, thus making them more vulnerable to drought.
The habitat of these forest giants spans a misty, 30-mile wide area down California’s coast, extending from Big Sur to slightly north of the Oregon border. As the sole living species of the Sequoia genus, these trees can grow nearly 400 feet tall and live for more than 2,000. It may surprise you to learn that fog plays an important part in tree growth. Redwoods have developed the ability to absorb up to 40% of their water intake directly from the fog. This is necessary because usually, a tree will move water from the roots up to the top of the tree; but given the size of the Redwoods, this root-to-treetop water movement is not possible otherwise.
Capturing the behavior of fog with computer climate models is not an easy thing to do; however, a recent modeling study hinted at the possibility of foggier coastlines due to global warming. Biologist, Todd Dawson, and his team wanted to see what, exactly, the historical records showed.
Typically, fog will roll in along the California coast quite often between June and September. The team wanted to determine how this summer fog changed over time. To do so, they analyzed hourly fog sightings that were recorded from 1951 to 2008 at two locations: the airport in Arcata, located at the north end of the trees’ range and also at an airport in Monterey, which is near the southern end. They considered any low-hanging cloud cover, which was at or below 1,300 feet, to be fog. The team discovered that over the past 58 years, the coastal fog decreased by approximately 1.3 hours per day.
The research team then collected temperature, humidity, and wind data from across California, Oregon and Washington that was recorded during the same period, to see if there was any difference between coastal fog and inland weather. Apparently, there was a noticeable temperature difference between the coastal temperature and temperature found 50 miles inland. According to Dawson, this difference creates a vacuum that “pulls the fog on land, so the greater the difference between inland and coastal, the more power it has in drawing the fog on shore”.
The relationship between temperatures provoked further research, dating back as far as the early 1900s, and included looking into both temperature and fog data of that time. The difference between coastal and inland temperature went down, mainly because the coast was heating up faster than inland, thus reducing the force that pulled fog in. It should also be noted that the warmer the sea water, the less likely fog will even form in the first place. These factors show that fog has decreased in the past century from 13.5 hours to 10 hours.
You may be thinking the study ends there, but it doesn’t. There is still one big thing left to cover: the trees. The team had to examine how warm, dry days affected the Redwoods. They studied months of data on water exchange and flow in the trunk of one redwood tree, located in the Grove of the Old Trees preserve. They discovered that foggy days kept the leaves from losing water, sap flow dropped, and the fog helped to lock in moisture. However, on clear, sunny days, the trees were more vulnerable to drought.
This can be compared to other studies on redwood water shortages. Dawson explained:
“We see dieback at the very tops of the biggest trees. At the other end of the spectrum, you can also imagine that if the soil gets drier and drier because there’s less and less fog, then the newest trees—the little seedlings that are germinating—they may not survive through the dry summer months.”
It is uncertain if climate change is to blame for the disappearing fog, but Dawson said that “it seems likely that it may be the case”.
You can find the full study in the journal Proceedings of the Natural Academy of Sciences.
By Heidi Marshall
I have been with GreenFudge for about a year now, but I've had a passion for Nature my entire life. When I'm not writing articles, you can find me out hiking, gardening, working on green craft projects, or taking photos for my website. You can check out the site at http://arkisaeo.com
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Tags: California Redwood, climate change, Coast Redwood, drought, fog, Redwoods, Sequoia, study, temperature, tree damage
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