I’m turning in a slow circle on Hawk Hill in Sausalito, tracking a mental panorama of the Bay Area. It’s a hyper-clear December day, and I can see forever. If not to the beginning of time, at least pointed in that direction — to the forces by which time makes itself known. It is possible to identify mountain peaks in the North, East, and South, (Tam, St. Helena, Diablo, Hamilton, San Bruno), with a long Western pause at the Pacific Ocean, where the Farallon Islands raise a jagged hand of rock. San Pablo Bay beckons deeper into the Bay Delta towards the great rivers connecting inland. The Golden Gate Bridge seems politely to introduce San Francisco Bay. The sparkling city looks artistically rendered, like a petroglyph. In the overall view, it is small. Geology and water rule.
The true sovereign reigns from the sky: the sun. Over vast stretches of time, sun-driven winds have helped erode those rocks into soil in which grow plants, again by way of the sun and photosynthesis. Plants power the rest of the food chain. California plant life is unique in all the world, thanks to the topography and the Pacific Ocean. It is host to native insects, reptiles, amphibians, birds, and mammals found nowhere else.
California is home to one of the greatest diversities of life on our planet — a natural hotspot for life and one of the most important landscapes for large-scale land conservation.
“Biodiversity” is a dull word for the generations of life forms and networks of relationships that make up the world in which we are embedded. In the vast oceans, life came to be about 3.7 billion years ago. Day after day, year after year, those microscopic beginnings evolved, increasing the numbers and kinds of life. Plants and animals adapted as mountains rose and continents moved. The view from Hawk Hill today came into focus about 8,000 years ago, and Native Californians were among the first Homo sapiens to witness it.
A California wrentit sits on a manzanita growing in serpentine soil. This is a scene you could have seen 20,000 years ago and is one you can see today — a testament to the long evolutionary history of the Bay Area’s biodiversity treasures. Image courtesy of Jane Kim
Today, biodiversity is in steep decline, with more than one million species headed to extinction. If we don’t change our relationship with nature, we will cause spectacular loss. Here in the Bay Area, we have a lot to lose.
The great mountainous features of California create a multitude of microhabitats, relatively small spaces with varying aspect to the sun, different temperature ranges and different precipitation patterns. Species co-evolve in these conditions, so many habitats beget many species. The California Floristic Province (defined by our plant life) is one of 35 biodiversity hotspots around the world. The Bay Area’s highly varied topography and proximity to the Pacific make it a hotspot within a hotspot — one of the most special places on Earth. In 1988, the Bay Area was designated the Golden Gate Biosphere Reserve by Unesco.
In 1989, British ecologist Norman Myers identified locations around the world rich in endemic species and also under intense human pressure. To qualify as a hotspot, a region must contain at least 1,500 endemic vascular plants. (Endemic means native and restricted to a certain place. Vascular refers to plants with roots, stems, and leaves that transport water and nutrients; nonvascular plants include mosses and lichen.) Hotspots are defined not only by what they have, but by what they’ve lost — at least 70 percent of their native vegetation. Myers’ concept provided environmental organizations with a map for focusing protection on the most biodiverse yet threatened places on Earth.
Take a look at a map of coastal Northern California and the Bay Area stands out, our nine counties arrayed around what might be called a figure 8 made by the joining of San Francisco Bay and San Pablo Bay. Here’s a significant stopover on the biotic superhighway along which nutrients flow from ocean to estuary to rivers to mountains and back around again, through the bodies of species including birds and fish. The great diversity of life forms arise from these cyclical interactions and are also sustained by them.
Underneath it all, the Bay Area is at a meeting point of two tectonic plates that move against each other, creating earthquakes, pushing up mountain ranges, concentrating minerals (like gold), and more. One result is California’s state rock, serpentine, visible in green-gray outcroppings around the Bay Area but most significantly at Coyote Valley. The 15 by two-mile stretch of serpentine at Coyote Valley supports owl’s clover and Plantago erectus, host plants for the Bay checkerspot butterfly (pictured at the top of this article). The Bay checkerspot owes its distinction as an endangered species to the widespread development of serpentine habitat. When species don’t have a place to live, they disappear.
The iconic western monarch butterfly is on the brink of extinction. Without careful monitoring and rehabilitation of critical habitats, we could soon lose this species forever. Learn more here.
In addition to the rocks, the water and the wind do their part to support Bay Area biodiversity, most powerfully in the cycles of the California Current. Annual winds push surface waters offshore, and water from the deep rises to replace it. Phytoplankton that has been lurking in the dark is now exposed to sunlight and photosynthesis does the rest. Blooming phytoplankton attract zooplankton to eat it; the zooplankton attract sardines and anchovies, and the chain of nutrition goes up the pyramid to the top predators, great white sharks that haunt the Farallones.
The California Current not only helps create one of the world’s richest marine ecosystems, but it also contributes to our plant diversity by helping to create our Mediterranean climate with cool, dry summers, fog near the coast, and wet, mild winters. Endemic plant life that find these climatic conditions just right grow here and nowhere else, including some species of oaks that create a unique ecosystem within their towering bowers.
The Bay Delta estuary, the largest freshwater interface between land and sea on the Pacific Coast of both North and South America, is on the precipice of a disaster long in the making. Millions of birds migrating along the Pacific Flyway have historically found food and water along the Delta’s spreading reach — almost all of which has been converted to agricultural and built development. We can’t continue to take so much from thronging life and expect it to keep creating the conditions that make existence possible for us.
People have availed themselves of the magnificent abundance in the Bay Area for at least 6,000 years, and Native Californians did so (and continue to do so) without domesticating wild species or driving them to extinction. The very functioning of our terrestrial ecosystem has been forged not only between rock and water but also by human intervention. Native Californians pruned, coppiced and most significantly deployed a staggered rotation of burning practices that increased yields of targeted plant species. It is likely that some of our most beloved endemic plants are still among us thanks to millennia of Native Californian care.
Today of course, our hotspot is a hot seat and we are most assuredly sitting in it. It is up to us perhaps first and foremost to see not only what is around us, but how it is changing in a dynamic process of creation and re-creation. There is plenty of biodiversity here to celebrate. Even in the city of San Francisco, 95 percent developed, we still have 500 endemic plants. These are stalwart witness to the long time frame, profound forces that give our human life context and joy.
About the Author: Mary Ellen Hannibal is a nationally acclaimed Bay Area science and culture writer and was a speaker in POST’s 2016 Wallace Stegner Lecture series. You can learn more about her work on her website.
Peninsula Open Space Trust (POST) protects open space on the Peninsula and in the South Bay for the benefit of all. Since its founding in 1977, POST has been responsible for saving more than 86,000 acres as permanently protected land in San Mateo, Santa Clara and Santa Cruz counties. Learn more