History

Cretaceous
145.5 – 65.5 million years ago

Estimates are still uncertain, but researchers now think that the first grasses arose at least 80 million years ago and began diversifying before India lost its connections with Africa and South America. Grasses found in fossilized dinosaur scat suggest that grasses may have first evolved in tandem with herbivorous dinosaurs.

Pliocene
5.3 – 2.58 million years ago

Grass pollen first appears in California’s fossil record and become widespread on broad wet coastal plains. The Coast Ranges (and other California mountain ranges) begin a major period of uplift (lasting from 5 to 1.6 million years ago) that creates a diversity of coastal, inland, and high elevation climates where grasses thrive.

Pleistocene
2.58 Million – 12 Thousand years ago

Climate Change

California undergoes dramatic changes in climate and geology that diversifies grassland environments. Mediterranean climate (dry summers and wet winters) is established in California with the arrival of cold off-shore currents. Uplift of the Coast Ranges (and other California mountain ranges) continues. Step-like coastal terrace prairies, a principal home for California’s coastal prairies, are created by changing sea levels. Coastal terrace prairies are estimated to be 80,000 to 600,000 years old.

Species Diversification

Grassland species diversity reaches astonishingly high levels. By the late Pleistocene (1.5 million years ago to 12,000 years ago), California grasslands supported one of the greatest wildlife assemblages on the Earth. Many native Californian annual and perennial forbs diversified during this period.

The diversity and abundance of pre-historic grazers, browsers, predators, and scavengers may be one of the greatest in the world exceeding that of East Africa. Mammoths may have been key agents in maintaining grassland biomes, converting forests to grasslands by destroying trees, and possibly creating vernal pools by wallowing.

The last 10,000 years

Humans crossed the Bering Straits in Alaska during the last Ice Age and migrated into California.

The earliest human remains dated in North or South American are from coastal California (Arlington Springs woman from the Channel Islands) when grassland megafauna were abundant.

At the beginning of the Holocene, the majority of the megafauna species went extinct. The exact cause is unknown, but may have been caused by hunting and intensifying summer drought.

Native Americans, who arrived in California by at least 10,000 years ago increased the fire return interval (caused by lightening strikes alone) from 1-15 years to an average of every 2 years.

Recent History

The arrival of Europeans in the mid 1700s transformed disturbance regimes (grazing and fire) and species composition in grasslands.

Grazing

Sheep, cattle, and horses were introduced into coastal grasslands by the Spanish Missionaries (~1769). Coastal prairies were considered prime property for cattle and sheep ranching since the early 1800s because of their productive native perennial grasses.

The demand for hides and tallow grew with the increasing size and number of settlements resulting in extensive hunting and slaughter of deer and elk in the early 1800s. Elk were locally extinct in Marin County by 1860 and extirpated statewide by 1873.

Non-Native Species

Most of the European exotic plants that are now established in California grasslands were probably first introduced into California in 1769 with the arrival of Father Junipero Serra, who established the first European settlement in San Diego.

Fire Suppression

Fire suppression began with the Spanish who prohibited Indian burning in grasslands because it interfered with the forage needs of their domestic livestock.