About the San Joaquin

Natural History

Excerpts by J. L. Medeiros
Great Valley Museum

Dawn came to break the chill of a short summer night. The concert of frog-music had ended while distant clucking sounds of ducks and coots became more frequent. A glossy blackbird with scarlet and yellow shoulder patches was perched on the long stalk of a cattail. His chirp was occasionally substituted by a shrill ka-reee. Before long, the orange sky was filled with flying silhouettes and the cheerful morning sounds of a lush marshland in the Great Valley. It was another July day where thousands of birds and animals would go about their specialized tasks of survival and reproduction.

A few miles away, sleepy farm children stirred to the clanking sounds of a tractor working in a nearby field. A crop-duster roared over the house on a low pass. It was no use ... a few extra winks of sleep were impossible.

It was a beautiful cool, crisp morning. Before long, the heat would be unbearable. The smells of the morning were almost overwhelming ... fresh mown alfalfa from the night before ... bacon frying for a sunrise breakfast ... a routine the children would not appreciate for many years.

Such was life not long ago for man and beast in the San Joaquin Valley. Even this has radically changed in the past few decades. Small farms are practically non-existent. Thousands of acres of homes, buildings and roads have carpeted the valley floor. This once-wild valley is now feeling the tremendous pressure from a runaway economy and population boom.

It cannot be contested that the Great Valley of California (the combined Sacramento and San Joaquin Valleys) is the most agriculturally productive region of its type in the world. Owing to productive soils and ample water from neighboring mountains, the valley has lead in agri-business for countless years. Fresno County alone has reported annual gross profits in agriculture-related products of more than two billion dollars (1980). The Great Valley feeds not only its own residents but today, supplies much of the nation and parts of the world with staple and luxury crops.

The economist might view the Great Valley as a massive gambling hall where millions of dollars are annually placed on various crops. The roulette wheel is regulated by weather and fluctuating market values. In some years, the casino may provide the players with great profits, making agriculture an attractive occupation. In other years, weather, drought, and unpredictable markets can destroy a farmer. This kind of insecurity has forced small, privately-owned farms to yield to large corporately-owned ranches. The "sustenance farm" is a vanishing concept; one that has high improbability to the Great Valley.

Hundreds of years ago it might have been easier to view the Great Valley from a strictly biological perspective. Today, a myriad of other non-biological factors play important roles in the reshaping of this vast area.

Geography and History

The Great Valley is a 400 mile long trough that varies in width from 30 to 50 miles. Although flat in general topography, it slopes gently down from the Sierra Nevada Mountains towards the West. It rises more abruptly into the Coast Ranges. Today the valley averages 5 to 20 inches of annual rain, falling predominantly between the months of November and February. Its latitude, topography and proximity to the ocean create a Mediterranean climate: hot, dry summers, and cold, wet winters.

Two major river systems drain the Great Valley: the Sacramento in the North and the San Joaquin in the South. These are fed by numerous tributaries, some of great size and volume. The discharge of these two main river systems is supported for the most part by the snow melt of the Sierra Nevada. Without this, the valley would certainly appear quite different. It is because of this enormous watershed that agricultural diversity and volume exists today.

Geologically speaking, the Great Valley in its present form is quite recent. Three to ten million years ago, the Sierra Nevada lifted to great heights and the Coast Range Mountains were being built. The Great Valley, although deposited as sediment millions of years before, was beginning to take its recent shape.

During the Paleozoic Era (more than 500 million years ago), the Great Valley did not exist, but was part of the ocean floor near the edge of the continent. Sediments from eastern portions of the continent were piling up here. Trilobites, fishes, reptiles and other creatures that evolved during this era (of 340 million years) were transformed to rocks and fossils.

In the Mesozoic Era, molten rock that would later become the granite core of the Sierra Nevada began intruding deep beneath this ocean floor. During the later part of this era, the Sierra began its gradual uplift. Parts of the ancient sediments were crumpled and lifted above sea level. Erosion became a dominant force and the granite of the Sierra was gradually exposed. It is estimated that sediments varying from 9 to 17 miles were gradually carved away.

As the Sierra was emerging from the sea, the Great Valley region was still submerged. However, the water was considerably shallower. It was rapidly being filled with sediments from the weathering rocks of the Sierra.

Life flourished in this shallow coastal area. The extinct Trilobites were replaced with crabs, clams, snails and ammonites. Feeding on this array of food were fish and ocean dwelling dinosaurs (Ichthyosaurs and Plesiosaurs). Later, as the Sierra Nevada rose even more, terrestrial dinosaurs elsewhere on the continent became extinct. It was a time of great change.

The Cenozoic Era was a period during which many life forms as we presently know them developed in North America. As early as the Paleocene (70 million years ago) the first mammals evolved. During the Tertiary Period of this era a tropical climate prevailed. Warm temperatures promoted lush plant growth in the West. A jungle-like ecosystem may have existed where eroding rivers joined lagoons in the sea. The Sierra, eroded into a series of rolling hills, was soon to be drastically uplifted. The Coast Ranges, although beginning to move, would await their major building.

During the late Tertiary, the Sierra Nevada began its major tilt westward. Faults formed, lifting the massive granite mountains. Earthquakes shook California and the Coast Ranges began their major uplift and folding. The Great Valley was beginning to fill with the eroded sediment of these mountains. (It was the beginning of a new topography for California ... and the beginning of an Ice Age that would greatly alter the face of North America).

The plants and animals that have evolved in California are a product of a changing geologic and climatic environment. In the past three million years, there have been numerous events, climatic, physiographic, and biologic that have set the stage for speciation. The earth became colder, ice and snow covered much of this continent, and mountain building continued. The Great Valley was beginning to take its present shape.

As the Sierra Nevada continued to uplift and volcanic activity continued sporadically, new river courses were delineated. They were wild rivers which carved valleys and eroded millions of tons of sediment. Many flowed in directions much different than today. They are now settled, at least temporarily, into their present courses. As they eroded, they repositioned most of the ten mile high mountain range into the Great Valley's basin. Today, on the western edge of the valley, it is not uncommon to find sediment depths equal to or more than that of old mountain elevations.

The tropical plants and animals of Tertiary central California were forced out by the changing Quaternary conditions. New species inched south from northern latitudes to stay ahead of the encroaching glaciers and cold. Other species came from the south, driven north by similar ecological factors. Central California received an assortment of plants and animals brought together by strong forces. Many species remained virtually unchanged. Others adapted and altered time and time again, until they were best suited for their new home in California.

Many feel that the Great Valley, prior to white man and irrigation, was a massive desert inhabited by the lowliest of insects and weedy shrubs. Although there were areas within the valley that were certainly desert-like, it was quite lush in more than an equal share of regions. Above all, it was a spectacular grassland with variety in vegetation and animal life. It was a truly wild place.

After the disappearance of the last large Sierra glaciers (10 - 20,000 years ago), the valley underwent many successional changes on its way to becoming a grassland-prairie. Many of the plants and animals that had lived here during cooler periods migrated out with the advancing heat and aridity. Some moved north, back to boreal forests. Others took a shorter route and sought refuge in the higher elevations of the valley’s surrounding mountains. What remained in the valley were drought-tolerant plants or plants that found rivers and marshlands as suitable homesteads.

Flora & Fauna of a Valley in Equilibrium

For thousands of years plants and animals competed for their own special niche or placement within the valley ecosystems. During the last 10,000 years, the climate became more stable and the Great Valley ecosystems approached equilibrium. They remained dynamic but stable for more than ten thousand years until 1769 when Europeans entered California to stay.

It must have been spectacular during previous years of equilibrium. Although grasslands were probably the dominant vegetational feature, there were also large oak woodlands, extensive marshlands, vernal pools, riparian forests and alkali sinks. These community types supported unique plants and animals, each with special ecological interrelationships.

Grasslands were the most extensive. Thousands of acres extended from the Coast Ranges to the Sierra Nevada and from the Tehachapis to the Klamaths. A great number of the grasses were perennial bunch grasses, much different than the sod-prairies of the Midwest. These bunch grasses were tall and stout. Many grew chest-high to a person. Interspersed with these were numerous annual grasses and a luxuriant assortment of wildflowers. Lupines, poppies, sunflowers, represented only a few of the thousands of flowering plants unique to California. On the margins of the Great Valley some peculiar grasses found refuge. These low growing, sticky grasses probably evolved on the beaches of ancient oceans in the Valley. As the sea receded, these plants remained in the pools and wet depression of Coast Range and Sierra foothills.

The grasslands were interrupted with unique topographical features: vernal pools. These were depressions filled with shallow water with impervious bottoms of clay or bedrock. These vernal or "spring" pools were filled by winter rains. Water could not percolate through but instead, evaporated away from the pool. By summer, these pools were once again as dry and hard as concrete. It was during this period of evaporation that a spring flora would emerge to decorate each pool with bold colors. As the pools dried, the volume of collected water was reduced. Instead of a single species following the declining water line, numerous species of various colors bloomed in concentric rings. Each was designed to best fit the various micro-environments of their shrinking pool.

In some years, the valley must have appeared as a solid sheet of colors. In as late as 1868, John Muir's first trek across the "Great Central Plain of California" left him awed with the "continuous bed of honey-bloom" and the lush river courses with tall oaks. Still today we hear stories of days-gone-by when spring wildflower displays were common and poppies grew wall-to-wall.

The flat aspect valley prairie was broken up by riparian and valley woodlands. Here the riparian plants grew, fed by the cool melt of Sierra snows. The woodlands were dense. Those that flourished close to the water contained poplars, alders, willows, box elders, maples and similar trees and shrubs. These woodlands were among the valley's finest wildlife preserves. Within them were found egrets, herons, hawks, woodpeckers, various waterfowl, and an almost unending list of birds. Along with this rich avifauna could be expected other participants in a well-balanced ecosystem; a lush understory of plants, insects, rodents, and larger mammals like raccoons, foxes, coyotes, and other predators. At the edges of these riparian jungles was a transition zone called the ecotone. It was made up of trees and shrubs not as tall as those near the water's edge. The ecotone was an essential buffer between the riparian and grassland communities.

Away from the immediate ecotone, the stately Valley oak woodlands clustered. Each summer as the snows of the high country melted, these oaks would be fed by river flood waters. Today the once-wild rivers of the valley are warm, slow and muddy. No longer do they flood the river margins and quench the thirst of the monarch oaks. Low water tables and voracious domestic cattle that graze on seedlings have doomed the Valley oak. As is true for many plants and animals of the Great Valley, it is destined for early extinction.

Water seemed to rarely be a problem for plants and animals near the San Joaquin and Sacramento Rivers. It was a time of great seasonal changes: wet winters, warm springs, hot summers and balmy autumns. The early summer=s heat would melt the Sierra snows while rivers flowed cold and wild until July or August. Passage across the San Joaquin River was impossible during its flooding stages. Often it was miles wide and could not be forded or ferried at its lower reaches. In years of heavy rain and snow, the southern San Joaquin Valley would be joined to the north by a continuous shallow lake. Tulare, Kern and Buena Vista Lakes would often combine during flood periods to produce a freshwater lake hundreds of square miles in area.

Excepting drought years (which undoubtedly spurred the claims that the valley was but a desert) this abundance of water from snow melt and rain supplied thousands of acres of freshwater marshlands. This expansive ecosystem was, without doubt, the most biologically productive of all within the valley. Marshes lined the river courses of the valley and were nourished by underground seepage as well as flood water. Here, in a relatively constant environment, plants could grow profusely and establish habitat for both aquatic and terrestrial organisms. Cattails, tules, rushes and sedges flourished in the slow moving water of the marsh. Under the water's surface, fishes, frogs, crayfish, clams, worms and crustaceans thrived. Innumerable insect species lived in the mud, attached to submerged stems, or in free-floating forms. A complex and involved ecosystem developed between primary producers (plants), primary consumers (herbivores), and a lengthy list of secondary consumers (carnivores and omnivores). As these organisms perished, their nutrients and energy was returned to the ecosystem via decomposing bacteria and fungi.

The marshes were the gathering grounds of millions of waterfowl. Special flyways evolved as ducks, geese and other migratory birds sought food and rest in the Great Valley. It is through the ecological principles of marshlands that officials develop game and wildlife refuge management principles today.

At the wide margins of the marshlands and flood plains developed the alkali sinks. Here water would accumulate infrequently and be left to stand and evaporate. It might be months or years between periods of re-flooding. Intermittent moisture levels and impervious clay soils encouraged the development of alkaline and saline regions within the valley. Because of this adverse environment, numerous plant and animal species evolved to tolerate its extremes: high temperatures, long periods of drought, and increased salts in the water. Saltbushes, salt grasses, and other peculiar plants developed mechanisms to either store or exclude salts. Rodents learned to scrape salt layers from seeds and leaves, excrete concentrated urine (to save water and rid of salts), or eat fatty seeds which provided more water through cellular respiration. It was in these regions of sparse accommodations that unique organisms such as kangaroo rats, kit foxes, and leopard lizards developed and somehow learned to thrive.

No one knows exactly what the Great Valley looked like before European man came to stay. We do, however, have enough scientific information to develop a pretty clear picture. It was a vast, sprawling plain of a great variety of vegetation and animal life. It was a mosaic of grasslands, marshlands and woodlands, topographically altered by wild river, shallow lakes, and pools. It must have been an Eden for its fauna: everything from insects to mammals. It once supported large herds of deer, Pronghorn antelope and Tule elk. There was even enough space for Grizzly bears to roam (a California variety now extinct). The valley supported huge flocks of herons, egrets, and similar large birds. Bald and Golden Eagles, hawks, and falcons represented organisms high on the food chain. The California Condor must have made frequent visits into the valley in search of food.

Human Impact

We might wonder what crossed the minds of the first white explorers in the Great Valley. It must have been a sight to see. But how could man change in two hundred years what was sculptured by nature in more than ten thousand? How powerful was this man that he could alter the biological course of evolution beyond recognition? Before him, thousands of Miwok, Maidu, and Yokuts lived without significantly altering the landscape. What needs and wants of this man could threaten this one of a kind valley?

In 1769, the first Spanish missionaries entered California near San Diego. The following year the Great Valley was described by a small party of Spanish explorers looking for an inland route to Monterey. Awed by the immense valley, they were perhaps the first to unconsciously condemn it ... they called it a pasture ... destined to be grazed by domestic cattle and sheep. And so began the rapid demise of the Great Valley grasslands. Later would come enough people and machines to turn the fertile soils, mow the tall oaks, drain the marshes, dam the rivers, and flood or plow the vernal pools.

The grasslands declined first. Hundreds of thousands of Spanish cattle and sheep overgrazed the native grasses. These plants were predominantly perennial bunch grasses. They evolved without heavy grazing pressure and were hence not well suited or adapted for this catastrophic event. The native grasses were rapidly reduced in population, size and vigor.

Along with introduced livestock came seeds of foreign plants, imbedded in hair and wool or stowed-away in supplementary feed. The native valley plant species were not prepared for human intervention in their evolution and consequently were quickly replaced by the introduced grasses and weeds. Most of these alien plants came from other countries with similar Mediterranean climates, making their takeover that much easier. In only a few decades it was near impossible to find where native species were not replaced by foreigners such as wild oats, foxtails, brome grasses, thistles, filaries and mustards. Man, his voracious livestock, and foreign plants had struck their first blow, hastening the death of this huge and wild refuge.

The Nineteenth Century brought with it fame and fortune for new Californians. Livestock profits greatly fluctuated as they were so closely dependent upon ample rainfall. But new opportunities quickly substituted the dwindling livestock economy. The foothills of the Sierra yielded enough gold to attract miners from throughout the country. The mountain soils were hydraulically mined by gold seekers and the valley's rivers were filled with waste. During this new California preoccupation, hundreds of businesses and enterprises sprang up. New towns required service lines and railroads began to cover the state.

The century also saw advances in agricultural practices. Diversified farming produced a wide variety of grains and crops new to the California markets. Dry farming was prevalent, but a few of the valley's acres had seen irrigation water. Although the natural valley was experiencing a great change, the final blow was not dealt until the widespread usage of irrigation.

Who could stop thousands of people from trying their hand at making a living here? It was a good life, too ... fertile soils, ample water ... the Great Valley was destined to become famous.

With the Twentieth Century came irrigation, electricity and mechanization. Acres of wasteland were plowed and flooded with Sierra waters. Grasslands became productive grainfields. Rivers were dammed and water courses diverted. Oak woodlands were harvested and vernal pools and lakes flooded for rice fields. Machinery and tractors evolved seemingly overnight ... and the Great Valley's wildness disappeared equally as fast.

With agriculture also came industry, a rapid-paced attempt to keep up with the ever-expanding population. Factories began to spring up almost as rapidly as homes and housing tracts. Then came highways, school yards, shopping centers, and thousands of acres of asphalt, concrete and air pollution ... a far cry from waving cattails and seas of native grasslands.

We face today the same survival questions we did one hundred years ago. Only today there are more people to whom we find ourselves responsible. But, how much natural land remains? How much land already converted to agriculture do we dare build structures upon? Does anyone really care about the valley's last remaining marshlands, river lands, or vernal pools? If we are really concerned about precious agricultural land, why do we build homes and industries upon it? Is there any way to slow or stop this rampant monster?

We must still rely upon our innate desire for solitude, tranquility, and peace of mind. It is best found in nature ... or in parks, under trees and near birds. We still have the opportunity to properly manage the few remaining natural areas within the Great Valley. Even if there are but a few acres here by the river ... a few there by the marsh, we must continue to impress upon each other the need for wildness…the need to watch the sunrise, to hear the blackbirds cackle, to smell the spring wildflowers and fresh winter mornings.

We can't count upon Emerson, Thoreau or Muir ... we have only ourselves.