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Drought-tolerant lawns could change LA’s climate

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A new study shows how alternative landscaping could bring hotter days and much cooler nights

In the midst of a severe and years-long drought, many Californians have been valiantly trying to conserve water by replacing verdant lawns with less thirsty forms of landscaping. From scattered gravel to artificial turf to wood chips, such drought-tolerant features helped the state (sort of) cut back on its water use amid a pretty darn disappointing El Niño.

But could drought-friendly landscaping be affecting Los Angeles’s weather?

Probably not right now, but a new study from researchers at USC suggests that if drought-tolerant lawns were more prevalent, they could have a surprising impact on the local climate.

Specifically, yards that consume less water could increase daytime temperatures by up to 1.3 degrees Fahrenheit, as KQED reports. Daytime temperatures in the more desert-like San Fernando Valley could increase up to 3.4 degrees.

That’s because irrigated lawns keep surface temperatures cool, which has an impact on the overall level of heat on a bright sunny day. George Ban-Weiss, one of the study’s authors, tells KPCC that the process is similar to the way that sweat helps to keep humans cool when it’s hot outside.

But don’t start ripping out those succulents just yet. The study also found that landscaping features that use less water could help to cool off nighttime temperatures across LA by an average of 6 degrees—a much greater difference than the daytime increase.

Now, many people might prefer a slightly cooler afternoon to a chilly evening, but temperatures are rising precipitously across the globe. And with those increases, comes a greater chance of heat stroke. Ban-Weiss tells KPCC that temperature drops at night are crucial to prevent heat waves from becoming deadly.

"Research has shown that when those nighttime temperatures don’t drop sufficiently, you end up having more deaths from extreme heat waves—which is actually the number one cause of death ... for weather-realted reasons," he says.

Of course, such dramatic changes in climate patterns would only come to fruition if nearly everyone in the LA area decides to give up their green lawn. The only way that’s likely to happen is if the drought gets bad enough that the Southland simply has no water available for irrigation.

Interestingly, though, the study also found that daytime temperatures could decrease ever so slightly if LA really committed to the whole drought-tolerant thing and replaced "all urban vegetation" with plants that consume less water. In that case, more robust sea breezes would help keep the city cool on hot afternoons.