Lecture reveals fascinating details on local ecosystems
At the Rossotti Ed-Zoo-Cation Center in Merced — located between Applegate Park Zoo and Kiddieland — community members enjoyed “Wildlife Communities and Ecosystems within 50 miles” presented on July 10 by Candace Sigmond of the Grassland Environmental Education Center.
It was part of a free lecture for adults taking place on the second Wednesday of each month this summer from 7 to 8 p.m. at the Rossotti Center, sponsored by the Merced Zoological Society in conjunction with the Merced Environmental Literacy Collective and the City of Merced.
How the region changed through the passage of time made an interesting subject.
Sigmond said, “The area was covered by ocean water at one time.”
This was during the Paleocene and Eocene time, and the water from the Pacific Ocean remained until two to three million years ago.
Gradually, the marine area became a fresh water area, according to Sigmond.
She commented, “The San Joaquin River used to be wide enough that two-story or three-story paddle boats could pass each other.”
She continued, “The last 40 years, we lost some wetlands, and we’re trying to rehab it for migratory birds and local animals. We have ecological preserves, but also urbanization.”
“What makes the difference to everything?” she asked.
“Water. It defines our habitat!” she exclaimed.
One of the key topics, besides the ecosystem of the Central Valley, was that of the mountain ranges on either side of it — the Sierra Nevada Mountain Range and the Coastal Range.
Sigmond described the Coastal Range as being formed 100 million years ago.
She said, “It is less high than the Sierras. We get moisture rolling across the Coastal Range from the Pacific Ocean. Snowfall is what provides us with water.”
She continued, “The Coastal Range is divided into five distinct zones.”
In the Central Valley, the heavy marsh changed from marine to swamp to savannah, with this last change taking place about 15,000 years ago.
She said, “The savannah was dry and hot and didn’t support the grasses it used to.”
According to Sigmond, about 10,000 years ago people from Russia migrated through the Bering Strait and “worked their way into the Central Valley.”
They were hunter-gatherers.
The large local animals competed with humans for natural resources.
The giant sloth, short-faced bear, armadillo and sabre-tooth became extinct over the decades.
Smaller animals came to the wetlands to live.
“Starting about 6,000 years ago, we began to have heavy clay soil that would hold water for long periods of time, and a Mediterranean climate characterized by cool, damp Winters and hot, dry summers,” she said.
Sigmond said the Sierra Nevada Range was formed 15 million to 10 million years ago by volcanic activity. The Sierra Nevada mountains are block mountains.
She described them as “high and tilted” and “very sheer on the east side” with “higher elevations in the south and lower in the north.”
A debate regarding the age of the Sierra Nevada Range has been going on for many years. For decades, scientists thought the mountains were relatively young, experiencing most of their uplift as recently as 3 million to 5 million years ago.
However, more recent studies have questioned that belief. Specifically, a key study by Stanford researchers which was published in 2006 and was based on the results of using a technique called hydrogen isotope paleoaltimetry, concluded the Sierra range reached its current elevation about 40 million years ago.