What is a rare
plant?
There are three kinds of rarity in plants. In one instance, plants might
be found widely distributed with only a few individuals at each site. Another
type of rarity is when plants are found in a limited number of places, but
there are many plants at each site. The last type of rarity is when plants
are found in a few places and there are very few plants at each site.
Why are some plants rare?
Rare plants occur naturally in the landscape around us for a variety of
reasons. Unique combinations of soils and climate often result in plants
specially adapted over time to these habitats. Plants that are particular
to a region or locality are called endemic species. The diverse and unusual
soils, climate, and geography of California has led naturally to a large
number of endemic species in our state. Many of these endemic species
have limited distributions and are rare as well.
Some plants also become rare as a result of the actions of humans. Activities such as road building, housing developments, recreation, dams, agriculture, and timber harvest can lead to alterations in and loss of habitat for species. In extreme cases, this can result in the loss or extinction of plant species.
Rare plants on the western slope of El Dorado County:
The Pine Hill Endemics 
Centering around Green Valley Road in El Dorado County is a soil complex
called the gabbro soil intrusion that covers approximately 30,000 acres.
The rocks from which the soil is made were originally formed deep in the
earth's crust from molten rock. These rocks were then lifted up to the
earth's surface as the rest of the Sierra Nevada was being formed over
the last 150 million years. The soil that is formed from this material
as it weathers is generally red, mildly acidic, rich in iron and magnesium,
and often contains other heavy metals such as chromium. Outcrops of serpentine
rocks also occur in the Pine Hill area. The soils that result from the
weathering of serpentine are similar to the soils from gabbro rocks.
Growing on these gabbro and serpentine soils are a suite of eight rare plants that are found almost exclusively in El Dorado County. These plants are commonly referred to as the Pine Hill endemics and are associated with black oak woodland and chaparral plant communities scattered from Cameron Park north to Folsom Lake.
Protection for the Pine Hill Endemics
Housing and commercial development have threatened the continued existence
of the Pine Hill endemics. Loss of the habitat that is important to their
persistence and the periodic fires to which they are adapted have contributed
to declines in the number of plants present. The concern about these plants
became so extreme that in 1996 five of the eight species were listed as
either threatened or endangered by extinction under the Endangered Species
Act.
A plan to protect these species has been developed by local interests and state and federal agencies. The conservation plan establishes five preserves located throughout the gabbro soil complex. The preserves are generally greater than 400 acres in size to allow for prescribed fire management and to provide a buffer from surrounding activities such as irrigation, applications of fertilizer and herbicides, and other human activities. In designing the conservation plan, it was important to have the preserve units distributed throughout the gabbro soil area so that all species occurred within at least two preserve units and the greatest variety of individual plants (in other words, genetic diversity) were included. The final conservation plan includes about 10% (3,000 acres) of the entire gabbro soil complex.
Why is it important to conserve rare species?
Wild plant species are the source of many medicines, industrial products,
and improvements to agricultural and horticultural species. They are a
bank of chemical and genetic information that humans may be very grateful
to have available in the future. Furthermore, native plants are integral
to the function of ecosystems. The air we breath, the water we consume,
and landscape we live within are linked in a fundamental way to the native
plants that surround us.
The Pine Hill endemics are an important part of the natural heritage of El Dorado County. Their intrinsic value as species besides our own and their aesthetic value as a part of an intact natural landscape also are important considerations for their conservation.
