I’ve been trying to research this question on my own but nothing on the internet has made me feel like I actually know the answer. I’m traveling in California, it’s mid-July, and I’m very curious about this. I recently took a train from San Jose to San Luis Obispo. It passed through Salinas, King City, and Paso Robles. Most of the landscape on this journey, aside from the farm land, is golden hills.
From what I gather, the hills are covered in a grass and this grass is oat grass, specifically a variety of oat grass that is invasive so it cannot tolerate the heat of midsummer whereas a native grass would be able to. How did this invasive grass get here and why? Was the land on these hills cleared for cattle to graze? Interspersed throughout these golden hills are hills covered in greenery; trees and bushes. This makes me think that that’s what all the hills are supposed to look like. Did they all once have that greenery? If so, when was the last time they were all green? Is it agriculture, wildfire, or climate that has eliminated the trees and replaced them with oat grass?
What I’m really trying to understand is… should there be efforts to re-forest these areas? Are the golden hills a sign that the ecosystem has been damaged? Would they be better off with greenery? Would drought impede those efforts?
In: Biology
Should there be efforts to re-forest these areas? You’ll have to **first specify** which area it is, that was once forest. Much of California’s land [has been an open patchwork savannah](https://www.kqed.org/perspectives/201007090735/how-our-hills-got-golden) since before humans arrived:
>Five hundred years ago, the sunny, baked hills above Livermore would have been greenish, not yellow. Perennial bunch grasses with taproots penetrating down 18 feet took full advantage of permanent groundwater. And the plants would continue to photosynthesize throughout the extended drought of our Mediterranean climate, maintaining their vibrant living color until the first invigorating rains of the autumn arrived.
But are the golden hills a sign that the ecosystem has been damaged? **Yes**. The hills originally weren’t golden, they were green. Livestock killed off the native grass, and invasive grasses were the only things that could survive the grazing:
>The most significant change in California’s biodiversity was the transformation of these bunchgrass-dominated ecosystems to the near total replacement by Eurasian annual grasses. The Spaniards brought horses, cattle, sheep and their attendant European barnyard weeds into California in the late 1700s. These aggressive, non-native, annual grasses could germinate, flower and fruit in the short growing season — and were already adapted to the heavy grazing of domesticated animals.
>**Wherever livestock was introduced, the new grasses quickly outcompeted and replaced the perennials** in an incredibly short period of time. This occurred so rapidly that there were basically no scientifically trained witnesses to record the startling conversion.
Would they be better off with greenery? Presumably, yes, if by greenery you mean the original native grasses. But I don’t know how to bring back that original grass.
Would drought impede those efforts? Presumably, yes. The old perennials had deep taproots to stay green year-round. If there is no water for them to find, then they cannot use that old advantage.
One small piece of good news is that in the valley you are talking about, Salinas Valley, land is [unlikely to subside due to drought](https://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=18850), “[d]ue to the types of sediments” in the valley. So perhaps if the aquifers are recharged, the perennials could be replanted.
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