OK, we put live salmon in trucks and bring them up river because of the drought. What are we willing to do to save another iconic species – the ancient giant sequoia trees in our own backyard?
We’re not there yet but if we have another extreme drought year like the current one, veteran forest scientist Nate Stephenson suggests human intervention like laying down a drip irrigation line below the Big Trees “could be on the table.”
Pictured: This sequoia showed more than 50% foliage dieback, which was unusually high — an extensive survey revealed that just 1% of all mature sequoias showed more than 50% foliage dieback.
Some sequoias still standing are 2000 to 3000 years old and clearly have known drought before.“We know the year 1580 was a bad one because some of the sequoia trees show no growth ring that year.” Still ”the current drought is the worst since we started to keep records 120 years ago.” adds Stephenson, a Three Rivers-based researcher with the USGS.
Stephenson adds the past two years have been not just very dry but extremely warm compounding the stress on the trees.
“Over the 36 years Ive been here its the worse I’ve ever seen.”
“Last fall we monitored foliage dieback on mature sequoias” and we concluded the trees were exhibiting a “smart response” by letting go of older branches but keeping the younger ones. Their survey discovered that “1% of all mature sequoias showed more than 50% foliage dieback.”
But now in this second year “we are more worried about the extent of die-off this fall – we may lose some of the older trees.”
To get a better picture of just how stressed the trees are UC Berkeley plant physiologists – experienced Big Tree climbers will be coming here in July to take a closer look while an aeril survey by plane takes high resolution photos to determine just how bad it is.
Thirsty Big Trees
Sequoias drink a lot of water. One recent paper said the 3240 year old President Tree (near the Sherman Tree) gulps 748 gallons of water every day during the growing season to supply all that wood plus its 2 billion leaves.
Stephenson says besides the sequoias the rest of the park’s forest is suffering a die-offs “at an alarming rate.” He adds,we have plots of trees where we see 10 to 20% dead or dying pines, firs and cedars at the lower elevations, 5000 to 6000 ft. He points to the Crystal Cave Road as an example where the damage can bee seen.
“Tree deaths right now are just off the charts.”
By contrast, Stephenson says trees in the upper elevation of the park 7000 ft and above are fairing better.
Stephenson’s research in the past has focused on the need for fire to sustain the health of a sequoia forest and says a grove where a controlled burn happened may now benefit as it faces the on-going drought.
”This is just preliminary” but it looks like fewer trees in an area where a controlled burn took place vs the more dense plantings in an area where fire has not happened can survive better since there is reduced competition for water as well as decreased pest pressure. The more open ground also makes it harder for disease to spread, he adds.
Regards the idea of applying drip irrigation for the trees,Stephenson notes while there is no active consideration right now – the obvious question remains where they would ”get the water” has to be studied.
This severe dry pattern “could be a dress rehearsal for what is coming” long term, worries Stephenson, with the prospect of climate change both reducing precip /snow and and warming the atmosphere, that one-two punch we saw in the past two years.
Sequoias grow in narrow elevation band of about 5500 to 6500 ft elevation, the lower end of the snow belt, where a declining snowpack is felt the most.With the trees getting little water this winter some of these giants could take a tumble this long hot summer.
Just 70 Groves
Also,the loss of Big Trees is felt more keenly considering there are not that many out there – only about 70 groves of them on earth – growing only right here on the western side of the Sierra – the highest number being in Tulare County.
Stephenson worries if climate change continues there might not be Big Trees here 100 years from now.
Sounding a similar note,Todd Dawson, a professor of Integrative Biology has found that the blue oaks (Quercus douglasii) at Berkeley’s Blue Oak Ranch Reserve near San Jose and the giant sequoias (Sequoiadendron giganteum) in the Giant Forest of the Sierra Nevada are so drought-stressed that they may begin to disappear from the landscapes they currently define says a December profile of his views.
“Those guys are suffering big-time this year because the snowpack was only 40 percent of normal. They’re seeing water stress levels that we’ve never measured before. We may lose them. Not right away—they live a long time, they’re incredibly tenacious and very drought tolerant. But again, are we going to reach one of these tipping points where our snowpack gets so low that the groundwater falls below the root systems of these trees and they begin to die?”
What can be done, asks Dawson?
Move To Oregon?
“We could intervene. We could go to Oregon and set aside land and say, “This is where redwoods will be in the next 500 years.” We may have to physically move organisms to new locations. I think that we need to talk about this because climate and land-use change is happening at such a rapid pace that human hands are going to have to come in at some stage if we don’t want to see things go extinct.”