I tend to enthusiastically and often uncritically embrace every new water conservation number, as if using less water is an unqualified good. I generally believe that, and you’re going to have a hard time pushing me off that intellectual turf. But there’s a flip side I’m trying to think through. It’s what economists might call the “non-market value” of the green stuff in our cities.
Ben Jones, a recent University of New Mexico economics graduate now doing a postdoc at the University of Oklahoma, presented some data as part of his recent thesis defense about the health and wellbeing values of urban trees. In particular, Ben was looking at the impact of the emerald ash borer, an invasive pest killing trees in the eastern United States. Loss of ash trees comes with a non-market cost that’s difficult but important to measure. There’s a direct health benefit as trees clean air, and a less direct but no less important benefit because green amenities make us happy. That’s why we plant and water stuff around our houses. Ben and UNM economist Shana McDermott* have a paper here that digs into the details. While specific to the eastern ash trees, they’re raising issues that are worth applying to our municipal tree coverage here in the western United States, where we’re in the midst of a vast undirected experiment in using less water in our cities. One result of using less water is having fewer trees. This comes with a cost that I don’t feel as though I’ve properly conceptually matched up against my unbridled enthusiasm for water conservation.
water conservation’s California costs
I was thinking about this hole in my thinking today while reading this Sacramento Bee op-ed by John Woodling, bidding us think about the tradeoffs associated with California’s impressive water use reductions:
These reductions have come at a cost.
Most notably, our trees and landscapes suffered as most water agencies limited irrigation to two days per week or less, even in hot, dry summer months. Our trees are an important environmental resource, a source of tremendous community pride and a gift from one generation to the next. Many of them are showing signs of severe stress, making them susceptible to pests and disease. Some have died or eventually will – a sad legacy that will extend far beyond this current drought.
* By way of full conflict of interest exposure, I recently lectured in one of Shana’s classes, for which she compensated me with a gift card to the Frontier restaurant, which funded a delicious and large burrito on Friday. #universitylife
“trees and landscapes have suffered”. But have you tried watering the landscapes even less, and applying enough of the saved water to the trees to keep them alive?
I have family in Sacramento and visit on a regular basis. That county has square mile after square mile of nice green lawns.
(There’s an old bureaucratic trick of imposing any cutback on the highest profile amenity, as to create public opposition to the cutback. It’s a shabby thing to do.)
John-
Excellent point, and one that hadn’t occurred to me either. Presumably trees in urban areas also translate into modest AC savings in summer (temperature, shade), and perhaps heating savings in winter (wind reduction). Energy savings also translate into water savings. All of these savings are likely small, but may tend to balance the water costs. Would be interesting to compare benefits of deciduous trees and evergreens. Assigning a value to intangibles like quality of life would likely be more dfficult.
BDZ
Francis has it exactly right. We could certainly water “smarter” for the trees, but I think there is still a lot more conservation to give, particularly in the Sacramento area.
Looking deeper into Woodling’s (member municipalities’) agenda: the true topic is growth (e.g. Folsom, Roseville, PCWA), and it is natural for them to fend off conservation requirements becoming more permanent. Local interests vs. smart policy. Follow the money. . .
Almost as refreshing as the sight of trees on a boulevard but much rarer : a public thinker willing to drop a seemingly contrary or awkward thought into his or her mind, see where it leads and then forthrightly describe the outcome to readers. This is one of the reasons I so much enjoy reading John Fleck’s musings on water and the hydrological part of human culture.
the shade and protection from the drying wind are very important things that trees do help with, but if a tree dies in this drought it could be replaced with a more drought tolerant and adapted alternative tree other than those commonly used…
After watching much of the SWRCB Urban Water Conservation Workshop yesterday, I had the following deep thoughts. It is often difficult to parse the policy alternatives and what they mean, since the discussion often goes into the weeds of the technical details of implementation across the diverse landscape. . . but the basic gist is this:
Of course, purveyors want more flexibility to sell, and use water as they see fit, without burdensome regulations. Most of the arguments centered around how they have invested $$$ in “drought-resilient” supplies or groundwater, or recycled, or desalinated water that they think should take them off the hook from the conservation regulations and required percent reduction. They have invested in assets to spend AS THEY SEE FIT. . . for reasonable political and economic reasons.
With a little attention, the trees should be fine.
Moving from the paradigm of short-term drought response, to considering the facts of long-term scarcity that are coming into focus now more than ever–the policy issue centers around the perceived right to use these assets (“developed” water aka “water rights”) for whatever urban landscaping or residential per capita per day fits a local lifestyle, at whatever water rates a local market is willing and able to pay. Is it possible to evaluate/weigh the societal value of reasonable and beneficial urban uses statewide? Or must we let these be determined locally?
How do we weigh the costs of imposing water savings – really the value of conserved water vs. the risk/impacts of not conserving? What is the benefit of conserved water for a community that would rather spend it? Is it all about this regulatory threat to firm supply for future development? (as I’ve suggested above)
When there is no longer a risk of public health and safety emergency, is there a value to maintaining conservation regulations for the sake of other beneficial uses? Should a water right be unfettered as the holder perceives its “face” value? Or should the state exercise its authority to a finer point?
The Brown administration, in renewing the drought emergency proclamation, is reaffirming that “something has got to be done.” This does not seem unreasonable when facing the continued lack of runoff and supply conditions to date. After the next big storm, will California still have the courage to face these issues?
The economic and environmental contribution of urban tree canopies has been studied and quantified for the City of Denver by the US Forest Service and UC Davis. Look for “Urban Forest Assessment for the City of Denver” by McPherson et al. That might be a good starting place to examine the issue you have raised.