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
I’m from the golden hills and was a Park Ranger in the Marin Headlands (GGNRA) and Sequoia NP in the foothills. You’re describing the ecosystems usually called oak chaparral and savannah. They are naturally there to some degree and there are many preserves and restoration lands that are focused on oak chaparral, Kaweah Oak Preserve is one I am familiar with in Visalia.
As the glaciers from the last ice age *continue* to recede there is a progression of changes to a landscape as the earth exposed and then broken down due to physical, biological, and chemical action. There are primary species that can rush in and take advantage of the harsh conditions, like alder. Then secondary and so forth move in as top soil builds up. Climate changes and so certain groups thrive in certain areas as things settle. Fire ecology plays a large role in expediting the transitions, and dendeochronologists have at least 15,000 years of history to reference in including extensive evidence of human intervention.
The California coast has experienced crazy changes even within human history, I was able to attend a lecture from a La Coast Miwok speaker who was sharing their oral history covered land 2 miles out from the current shoreline in SF and about 350ft below current seal level. There used to be a huge waterfall where the golden gate bridge is!
Weather patterns between the coastal range and the Sierras are pretty simple, moist air is compressed on the windward side of the coastal range creating a rain shadow on the leeward side, so long hot dry weather. Turns out oaks and grasses love those conditions.
I live in Minnesota now and the boreal ecosystem is moving north, northern MN is now sub boreal, and the oak savannah of southern MN is migration north, followed by prairie/grassland.
As for “invasives” you can go join the Sierra Club for talking points on that.
The true ELI5/TLDR: The planet is covered in moving plates. Plates push together and form big wrinkles. When you blow cool moist air over those wrinkles, the moisture falls down and hot dry air continues to blow past them. Only some plants like hot dry conditions. In California, those are oaks and grasses, we call that an oak chaparral or savannah. It’s natural, and even if you miss big trees, don’t plant them please.
P.s. just because I was a park ranger for 6 seasons doesn’t mean I know shit.
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