Native Shrublands: Past, Present, and Future

It is interesting to think about what natural California was like in the past, and sobering to consider its future. Below are several photos that will offer a few point/counterpoints when discussing how to treat the nature we have left.

The loss of native shrublands has likely been significant over the past thousand years or so, due first to Native American burning, then over-grazing and burning by Spanish and Mexican ranchers, followed by American ranchers and farmers. Non-native weeds and grasses found theseĀ  heavily disturbed environments ready to colonize.

Although we do not have accurate records of what California’s landscape looked like prior to the arrival of humans, we do have images that record our impact prior to the massive development in the 20th century.

Old Mission SD c.jpgMission Valley, 1890s, and the old San Diego Mission. Note denuded hills in the background and the rocky earth in the foreground, likely the result of excessive over-grazing, fire, and wood collecting. Hwy 163 now goes through the gap in the hills on the left.

Old Mission Modern bMission Valley, 2008. Note the recovery of native vegetation on the hills in the background as compared to the first photo. The mission is obscured by surrounding development.

Mission Dam Old b2The old mission dam on the San Diego River, approximately 1920s.

Mission Dam b.jpgThe old mission dam, 2008. The hills in the background remain dominated by non-native grasses as they were in the 1920s, while the foreground above the river appears to have lost additional native shrub habitat.

Type converted front range II.jpgIncreased fire frequency has eliminated most of the native habitat in the front country of the Angeles National Forest, replacing it with non-native grasses. Remnants of sage scrub and chaparral still cling on in isolated arroyos.

Trabuco Dist Type Conversion fuel break.jpgFire managers often purposely type-convert native shrublands to non-native grasslands in an attempt to create “fuel” breaks. Ironically, these areas are much more flammable than the original plant community due to the presence of flashy fuels. Photo: Trabuco Ranger District, Cleveland National Forest.

Untitled a.jpgOver-grazing has created and maintained a rangeland environment filled with non-native weeds and grasses with a few old oak trees scattered across the landscape. Oak saplings that do manage to emerge are eliminated by cattle. Photo: San Luis Obispo County.

Untitled IIa.jpgA relatively undisturbed oak woodland with a sage scrub understory. Note the mixed-aged oaks in comparison to the previous photo. This likely represents what much of the type-converted landscape of San Luis Obispo County once looked like.

Oak Woodland IIThis is one of the few, remaining natural oak woodland/grasslands in Southern California. Native purple needle grass and deer grass dominate this landscape of shallow clay soils on top of an ancient, basaltic lava flow. Native grasslands are typically found on such soil types, hence their restricted distribution. Photo: Santa Rosa Plateau, Riverside County.

What does the future hold? With climate change, native shrublands are predicted to disappear in the southern part of California, probably replaced by non-native grasslands. Areas that will become more suitable for chaparral are predicted to move northward. Whether or not chaparral will be able to successfully colonize those areas remains to be seen.

Climate Change CA bThe Thorne paper on the impact of climate change in California is available here.

There is often a debate over how much grassland there was in California prior to the arrival of Europeans, and where and how frequently Native Americans burned to create and maintain grassy landscapes.* However, discussing what the past landscape looked like, while interesting, is not particularly helpful when making decisions about how to preserve what’s left of California’s natural environment today.

If we want to preserve “cultural landscapes,” then sure, we can over-burn native habitat as Native Americans likely did and create vast, grass-dominated areas. The problem is that now, those areas will be overwhelmed by invasive weeds, not native purple needle grass.

And yes, it is reasonable to assume that Native Americans burned areas over and over to eliminate the natural vegetation communities in favor of those that improved survival. Shrublands are not the most conducive environments to make a living from, for humans anyway. That said, there’s enough disturbance on our landscapes already.

The basic problem with the hypothesis that grasslands once dominated much of Southern California and the central coast is that it is utilized to support the notion that native shrublands are unnatural and need to be mitigated. We confront this all the time in land management documents, court testimony, and casual conversations. While it is fading as its adherents fade away themselves, it still has significant support because it confirms the biases of land managers, ranchers, developers, and fire managers who see chaparral has something they want to eliminate.

We have enough of a challenge in dealing with the impacts of climate change on native plant communities. We don’t need to add to it by increasing disturbances to protect cultural landscapes that were by definition, artificial and destructive of native species.

* A good paper that reviews the impact Native Americans had on the central coast can is: Keeley, J.E. 2002. American Indian Influence on Fire Regimes in California’s Coastal Ranges. Journal of Biogeography 29: 303-320.

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

%d bloggers like this: