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Course: Biodiversity | California Academy of Sciences > Unit 3
Lesson 1: Biodiversity Hotspots- What is a biodiversity hotspot?
- Biodiversity hotspot case study: California
- Biodiversity hotspot case study: Galapagos
- Biodiversity hotspot case study: Gaoligongshan
- Biodiversity hotspot case study: Madagascar
- Biodiversity hotspot case study: Mesoamerica
- Biodiversity hotspot case study: Philippines
- Biodiversity hotspot case study: Sao Tomé
- A closer look at a California hotspot area
- Test your knowledge: biodiversity hotspots
- Exploration questions: biodiversity hotspots
- Activities: biodiversity hotspots
- Glossary: biodiversity hotspots
- Selected references: biodiversity hotspots
- Answers to the exploration questions: biodiversity hotspots
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A closer look at a California hotspot area
Sierra Nevada: Range of Snow and Ice
Note: This article is taken from material prepared for the 2005 exhibit at the California Academy of Sciences called “Hotspot: California on the Edge.”
The Sierra Nevada, which means “snowy range” in Spanish, stretches 400 miles (644 km) along California’s eastern flank. It is bounded on the west by the Great Central Valley and on the east by the Great Basin. In cross section, the Sierra is shaped like a triangular wedge, with a much steeper slope on the east side than the west.
About 1.8 million years ago, after the Sierra Nevada began to rise, the Earth’s atmosphere turned cold, marking the beginning of the Pleistocene, the last ice age. Glaciers grew high in the mountains and moved slowly down former stream channels, carving U-shaped valleys as they advanced. Small glaciers still exist at the highest elevations in the Sierra Nevada, where they continue to scour the landscape. The plants and animals that live at high elevations have special adaptations for surviving the cold, harsh environments.
PLEISTOCENE
About 1.8 million years ago, the last ice age began. A period of long-term cooling of Earth’s climate resulted in the expansion of continental and polar ice sheets and mountain glaciers.
As much as 30% of all the continents were covered by glaciers and parts of the northern oceans were also frozen.
During this ice age, no massive ice sheets covered California. Glaciers were confined to high mountains, advancing and retreating 4 to 7 times.
The last ice age ended just 10,000 years ago, but several small glaciers still persist in California at high elevations.
BEAR & CONDOR
A species that lived during the last ice age and still persists today is called a Pleistocene relict. Its present-day distribution is a remnant of its wider range during the last ice age. The grizzly bear and California condor are both Pleistocene relicts – one is extinct in California, the other is barely clinging to existence.
California condor Gymnogyps californianus
They once ranged widely over the dry foothills and mountain ranges of central and southern California where they nested in caves and cliff overhangs.
Destruction of habitat, poaching, and lead poisoning led to the California condor’s decline. By 1985 populations plummeted to fewer than 9 birds in the wild.
At that time, conservation biologists decided to capture the remaining birds to protect and breed them.
Captive breeding programs have released birds back into the wild, but their long-term survival is still in question. Today [2005], 85 of the 222 birds in existence, are in the wild [The population estimate in May 2013 was 198 birds in captivity and 237 in the wild for a total of 435]. The California condor is the largest land bird in North America. An adult can weigh up to 25 pounds (11 kg) and have a wingspan up to 9.5 feet (3 m). Condors can soar for hours at altitudes of 15,000 feet (4572 m), cover hundreds of miles, and reach speeds over 55 mph (89 kph). Like most other vultures, condors eat carrion.
Grizzly bear Ursus arctos californicus
Grizzly bears once roamed the valleys and mountains of California, probably in greater numbers than anywhere else in the continental United States. It was the largest and most powerful mammal in the state.
Fueled by the discovery of gold, California’s population grew rapidly and humans and grizzlies came into contact more frequently.
Less than 75 years after the discovery of gold, every grizzly bear in California was gone. The last wild grizzly was killed in 1922.
The story of “Monarch” Monarch was captured from the wild and died of old age in captivity in 1911. After his death, he was donated to the California Academy of Sciences by the de Young Museum. He remains a legacy to the once mighty California grizzlies.
The California grizzly bear was designated the official state animal in 1953 and appears on the state flag.
CONCERNS
Fire Suppression - Restoration of natural fire cycles is important to restoring and protecting biodiversity in the Sierra Nevada. After a fire, the sequence of recovery of native plants provides wildlife with a variety of ecological opportunities.
Global Warming - As concentrations of greenhouse gases in the atmosphere increase temperatures, glaciers are retreating at an accelerated rate. California’s small mountain glaciers are particularly sensitive to warming.
Conservation - In 1913, after a bitter battle, Congress gave San Francisco permission to dam the Tuolumne River at Hetch Hetchy Valley in Yosemite National Park. Following this action, legislation was passed that made it illegal to ever put a dam in any national park again. Studies by the University of California, Davis show it may be possible to restore the valley by impounding Tuolumne River water at existing dams further downstream.
Want to join the conversation?
- I lived in extreme north coastal California for several years and there are definitely bears in the forests there. Are they different from the California grizzly?(7 votes)
- In California, the only species present now is the American black bear. This is the smallest of the three bears found in North America and individuals are not always black. The grizzly on the state flag has not been found in the state for nearly 100 years. http://www.defenders.org/black-bear/basic-facts(8 votes)
- Why it the scientific name for the Grizzly bear (Ursus arctos californicus) not in the standard binomial nomenclature?(5 votes)
- The Californian grizzly is a subspecies, therefore it is referred to by a trinomen, as opposed to a binomen. Source: http://en.wikipedia.org/wiki/Subspecies#Nomenclature(5 votes)
- Were there other factors that led to the extinction of the California Grizzly than what is mentioned in the article? Although the states population grew rapidly, there had to be large unpopulated areas remaining in 1922 unless Grizzlies were only found in specific, small habitats.. Seems more like active hunting than incidental contact with humans might be more to blame. Were there other changes to habitat caused by human or other non-human factors?(2 votes)
- Exotic species, including cats were hunting competitors. Much habitat has been destroyed,
"progress" turning natural land into human structures and roads.
Of course stupidity remains the primary cause of the many bears killed by humans.(1 vote)
- Yes. In fact some of them managed to mate with polar bears!(2 votes)
- How did the sower of the flag get a visual of the flag? Did they kill the bear, and then paint it on to present with the flag?(1 vote)
- No, the flag was made in 1846, before the extinction of the grizzlies.(1 vote)
- Are the grizzlies now living in northern British Columbia, Yukon, Alaska, and those that are considered nuisances around the Hudson Bay area?(1 vote)
- Yes. In fact some of them managed to mate with polar bears!(1 vote)
- I lived in extreme north coastal California for several years and there are definitely bears in the forests there. Are they different from the California grizzly?(1 vote)
- why are they animals in one area and not in the other.(1 vote)
- Animals can't survive in all environments because they don't have the right traits for that environment. For example, a polar bear wouldn't survive in a desert because it can't find enough food or water. Also, an alligator wouldn't survive in saltwater because it doesn't have the right traits for it.(1 vote)
- why is their only 8 infibiem in the island.(1 vote)