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TREES, PLEASE! Paving Paradise

By Robin Y. Rivet, for Let’s Talk Plants! August 2023.

“They took all the trees Put 'em in a tree museum And they charged all the people An arm and a leg just to see 'em…” © Joni Mitchell – 1970

YouTube video link of Joni singing Big Yellow Taxi.

Did you know that a study from 2010 by the American Planning Association estimated that Los Angeles County had approximately 200 square miles of parking lots? It’s an enormous amount of pavement, which typically has few trees. In fact, it’s enough area that a national study suggested that when street parking spaces are included, some cities may actually have as many as 8 spaces for every vehicle. Public data for our county is incomplete, but imagine how many square miles of paved parking are in San Diego? Assuming it’s not quite a proportional equation, (given our slightly geographically smaller and less congested region), a guesstimate might be approximately 150 square miles of paved parking. In fairness, Los Angeles also paved its riverbed, and thankfully, we did not; but we don’t deserve bragging rights - just yet.

Believe it or not, back in 1988, the City of San Diego adopted a council resolution advising a 50% shading policy in parking lots (see page 8) within 15 years of planting, and those performance standards were updated in 2006. So, where did the trees go? In 2019, several tree advisory groups reviewed the municipal codes that expected parking lots to have considerable shade, but found enforcement was sorely lacking. Additionally, the County of San Diego’s Parking Design Manual also has requirements that every parking space should be within 30ft. of the trunk of a tree, but that’s not happening either. The worst offenders seem to be municipal, military lands, strip malls, and even transportation hubs. Then there’s overly paved places that ought to care more about people’s needs - like houses of worship or school districts. Even Balboa Park’s large zoo lot suffers from excessive paving, but few trees. Unfortunately, when no one is looking, shade trees are omitted during development planning stages, get hacked or are subsequently removed. Why manage a few remaining trees when it seems expeditious to just pave them over? Last fall on one of the hottest days in September, the beautifully shaded University Square parking lot on University Avenue between 58th - 60th Streets lost over 50 mature Tipu trees - overnight. It’s become an urban crisis.

It’s not just California either. An area the size of Ohio was deemed impervious across the US in 2004. This not only increases urban heat islands but reduces groundwater recharge. Obstacles can be addressed. The need for PV should aim at commercial roof installations, but fewer parking lots, since trees cannot grow very well on top of buildings – and unshaded roofs continue to magnify heat. This article from a colleague in Davis nails the complicated issues and offers some thoughtful solutions. Ultimately, we’ll also need more street and private yard trees, plus more green parks as well as greener parking lots in our cities, but we must get started.

What if there was a statewide or even nationwide effort to de-pave? Most parking lots have room for many more, and larger trees; but developers who initially agree in principle to comply with municipal design, seem to find it convenient to shirk their responsibilities later. Citizens can provide the vision, report scofflaws and demand action from their representatives.

“… Don’t it always seem to go That you don’t know what you’ve got ‘til it’s gone They paved paradise And put up a parking lot.” © Big Yellow Taxi - J. Mitchell

Member Robin Rivet is an ISA Certified Arborist & UCCE Master Gardener – contact her:


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