I love redwood trees. I doubt there is anyone who doesn’t. So, you might wonder why I am going to tell you why planting more of them in our public parks in the San Francisco Bay Area isn’t a good idea. Read on…
History of redwoods in California
The native range of redwoods is very small. According to the US Forest Service, “The redwoods occupy a narrow strip of land approximately 450 miles in length and 5 to 35 miles in width. The northern boundary of its range is…in the Siskiyou Mountains within 15 miles of the California-Oregon border. The southern boundary of redwood’s range is…in the Santa Lucia Mountains of southern Monterey County, California.”
Many redwoods were destroyed for timber and many to clear land for other purposes, such as roads, agriculture, and development. However, the primary reason for its small native range is the demanding horticultural conditions required by redwoods. They don’t tolerate wind, particularly salty wind from the ocean. They require a lot of water. Where there isn’t enough rain, summer fog compensates for inadequate water. They need well drained soil and plenty of space to grow to their prodigious size of over 200 feet.
Because of these horticultural requirements, there weren’t many redwood trees in the San Francisco Bay Area prior to settlement by Europeans in the 19th century. There were no redwoods in San Francisco where the soil was sandy and strong wind from the ocean is salty. In the East Bay, the pre-settlement redwood forest was less than 5 square miles. (1) In fact, only 2.3% of pre-settlement Oakland was forested and redwoods were a small fraction of the tree cover. (2)
Trying to defy nature
Despite their demanding horticultural requirements and the historical evidence of these limitations, redwoods are often planted where they cannot survive because they are beautiful, popular, and “native” to California. As the climate changes, rising temperatures and drought have killed many of the redwoods that were planted in the past. As the climate continues to change, the future of redwoods in California becomes even more doubtful.
San Francisco’s 2017 Annual Report of the Urban Forestry Council reports that redwoods planted on public land in San Francisco are dying:
“Agencies such as SFO [San Francisco Airport], Zuckerberg General Hospital, and SFSU [San Francisco State University] reported concerns with declining health of redwood trees under their care. This iconic California native tree is not drought tolerant and current research shows that specimens planted in landscape settings outside their native areas are suffering from water restrictions and irrigation with non-potable water throughout the Bay Area. Redwood trees’ water and other cultural needs should be considered when planning future plantings since periods of extreme drought are expected to continue as the climate continues to change.” (page 11)
We see similar examples of planting redwoods in East Bay Regional Parks, where they are dying. Redwoods were planted at Lake Temescal about 5 years ago. Despite the fact that many of them are dead, the Park District continues to plant new redwood saplings adjacent to their dead relatives. Although it is a relatively sheltered area, the trees may have been killed by salty irrigation water.
The growing gap between science and public policy
On March 10, 2018, I attended a conference about resiliency in Davis, California: “Deepening our Roots: Growing Resilient Forests.” I went to hear Greg McPherson speak because I have read many of his scientific publications and I admire his work. McPherson’s research at the US Forest Service about the economic value of ecosystem services provided by urban trees (carbon storage, reduction of energy use for heat/cooling, increased property values, removal of particulate pollution, etc.) has been vital to those who defend our urban forest.
McPherson lives in Davis, where he is conducting a 20-year study about the urban forests of the future, i.e., those that will survive predicted changes in the climate. Three years into the study, his research team has made some preliminary recommendations for the trees that are likely to survive anticipated changes in the climate. None is native to Northern California. Most are foreign, particularly Australian.
McPherson also showed photos of trees being planted now that are destined to die in the near future. One was a densely planted row of redwoods in a median strip in Davis. Professor Arthur Shapiro, who lives in Davis, made this comment when I told him about McPherson’s presentation, “Redwoods are the walking dead here. I’ve known that forever and a year.” McPherson said redwoods have no long-term future in most of California. None of the public land managers in the Bay Area seems to know that.
East Bay Regional Park District ignores reality
East Bay Regional Park District is making a big investment in expanding redwood forests into places where redwoods did not exist in the past and where they are unlikely to survive in the future. They are clear-cutting non-native trees and creating visual screens on the periphery of the clear-cuts by planting redwoods along the trails. This photo was taken in Sibley Volcanic Reserve in March 2018 (the area is larger than shown in this photo):
These are areas that were a part of EBRPD’s “Wildfire Hazard Reduction and Resource Management Plan.” The Fuels Management Prescription for this Recommended Treatment Area was supposed to thin the eucalyptus trees to spacing of 25 feet by removing only small trees with trunks less than 10 inches in diameter. The original plan for this area did not include any replanting of trees.
The recent implementation of this project suggests that EBRPD’s strategy for tree removals has changed. At least in this instance, the trees have been clear-cut, not thinned. And redwoods were planted where none were originally planned.
It is always risky to speculate about the motivations of other people, but I will venture a guess about this new strategy. The Park District’s commitment to destroying non-native trees seems to have escalated from thinning to clear-cutting. And the public’s opposition to the destruction of trees seems to have convinced the Park District that they must plant native trees to replace the trees they have destroyed.
Unfortunately, the Park District does not seem to have taken the changing climate into consideration. The redwoods may survive long enough to placate the public, but they are unlikely to survive in the long-term. It is a good public relations strategy, but not a good strategy for a landscape in transition in a changing climate. It is also not a responsible strategy, given that the carbon stored by the trees being destroyed will contribute to the changing climate and won’t be replaced by dead redwood trees.
(1) Sherwood Burgess, “The Forgotten Redwoods of the East Bay,” California Historical Society Quarterly, March 1951.
(2) Nowak, David, “Historical vegetation change in Oakland and its implications for urban forest management,” Journal of Arboriculture, 19(5): September 1993
Conservation Sense and Nonsense 
I object to the snide nature of the headline of this post but what it says about planting redwood trees in unsuitable habitats makes sense, and I am surprised the East Bay Regional Park District doesn’t acknowledge this. If your speculation is correct, it shows it is not a good idea for an authority with presumed ecological knowledge to yield to pressure from a public with little ecological knowledge. However, I still balk at the idea of planting non-native trees, especially those from as far away as Australia, using the argument that these will be best fitted to deal with climate change. I am not saying that the aliens won’t grow, I am saying, should they be grown? It is a moral question as much as anything. Should we be interfering to this extent with the natural distribution of species?Surely there are local, native trees that could be planted instead. What about the Monterey pine, Pinus radiata? It is now rare in California, but grown extensively as a forest tree in Australia and New Zealand.
That’s an interesting mash up of arguments. On the one hand we are instructed to respect “ecological knowledge.” On the other hand, we are instructed to ignore “ecological knowledge” if it is contradicted by a “moral question.”
Here on Million Trees, we are primarily interested in practical matters. We need trees because of the ecological functions they perform. Therefore, we are solely interested in which species of trees are capable of living here. We don’t care where they are from. Much like our human immigrants, all trees are welcome in our world.
I like Monterey pines and they require less water than redwoods. They are native to a very small region about 100 miles from the San Francisco Bay Area. For that reason, the nativists don’t consider them “native” to the San Francisco Bay Area. They are therefore being destroyed by the projects the nativists demand. If Million Trees were interested in moral arguments, we might say that it seems immoral to destroy trees that are native to our region with a similar climate. (Monterey pine is grown for timber in New Zealand and is as unpopular there with nativists as eucalyptus is here.)
“We don’t care where they [trees] come from…” That sums up the difference between MillionTrees and me. I am a botanist and I am interested in understanding the natural distribution of species, not those that have been heavily influenced by Man’s tampering and interference. (Of course, this has already happened to a large extent, greatly confusing the picture of nature.) My approach to climate change is to try to mitigate it to allow native species to adapt gradually, rather than try to accommodate it by guess-planting a bunch of alien trees willy-nilly.
Of course, defining what is native is somewhat arbitrary, according to what geographic area you are speaking of (usually it’s a country or continent, such as “native to Europe” or “native to Africa” but it can also be to a region, as you say “native to the San Francisco Bay area.”) and also the time scale. In New Zealand many of the species considered native immigrated there from transoceanic continents because so much of the NZ land mass was inundated millions of years ago, but these natives grew in the original Gondwanaland supercontinent of which NZ was once part; they are clearly different from the alien flora from Eurasia and South Africa that immigrated through human agency and that in some cases threatens the native flora. I can assure you that a good deal of botanists’ time is taken up trying to determine the origin of plants, both genetically and geographically. It doesn’t help that humans are breaking down all kinds of natural barriers, with consequent loss of biodiversity.
You say, “My approach to climate change is to try to mitigate it to allow native species to adapt gradually…” Unfortunately, the fact is, we are NOT mitigating climate change fast enough to maintain historic native ranges of plants. There are many, many studies about the changing ranges of plants and animals. We should celebrate their movement because it improves their chances of survival. Demanding that they stay where they were 400 years ago is handicapping them further.
In fact, all the continents were once fused into one continent, Pangaea, when many life forms evolved. That’s why many plants that are presently considered native in one place are closely related to plants in distant places. Here’s an article about just two examples of plants that are not considered native in their present locations, but in fact existed there in deep time. https://milliontrees.me/2011/12/20/pangea-the-first-but-not-the-last-globalization-of-ecology/
Your theory that plants in New Zealand “immigrated there from transoceanic continents” is called vicariance. It is a discredited theory that has been disproved by the advent of molecular analysis. Here’s an article about how plants and animals have moved from one continent to another without the interference of humans: https://milliontrees.me/2014/05/19/the-monkeys-voyage-how-plants-and-animals-are-dispersed-throughout-our-planet/ Dispersal of species has occurred naturally for millions of years and it will continue to occur. In most cases, it’s difficult to distinguish a human dispersal from a natural dispersal, which is one of many reasons why it is largely pointless to try.
I love your post and wise response. Thank you! This is so important to share.
I keep arguing that Monterey Pine are native all over the Bay Area, based on fossil evidence, but that problem is, as you said, that they are on the nativists’ hit list.
Ironically, the magnificent Monterey Cypress isn’t in that hit list, and was actually used in an EBRPD promotional. Could it be the nativists are confused? We know they are hypocritical about who they like and who they want to kill.
I’ve been observing the change in Redwoods here since I became a gardener in the early Seventies. I was curious to see them in England, which makes sense because of the rain.
But they are clearly suffering here, as you said, because they need a lot of water. They would have a better chance if their old and enormous friends had not been killed for profit (another reason every human should use caution and think before cutting down any tree) because the Old Growth forest provides the humidity and protection and, some would say (after reading Peter Wohlleben’s “The Hidden Life of Trees”), love to help nourish their young saplings. Except for the tiny stands remaining, all they have are other traumatized young trees (a hundred years is young for these beings) to try to survive even in their former homes, such as an increasingly warming Redwood Park in Oakland.
Besides planting every tree who has a chance to survive here, like Acacias, Eucalyptus, etc, I keep recommending they try native drought tolerant and exquisite Pinus Sabiniana as well as Coulter Pines, Bishop Pines, and other lesser-known local conifers.
And especially drought tolerant Douglas Fir who can match Redwoods in height and who help create a wonderfully diverse understory of wildflowers, mushrooms, etc.
Even better would be to plant Douglas Fir each time they plant redwoods since they seem to be very compatible on Mt. Tamalpais and elsewhere, with the Psuedotsuga helping Redwoods with moisture and fog drip. I like to believe they are friends since they act like they are.
It’s worth a try, but will the park agencies? Not likely when they so enjoy and profit from clearcutting and poisoning.
I had heard of the tree killing at Sibley’s and so have avoided going. That photo proves it’s far worse than I’d thought. Criminal to kill such beautiful healthy trees….