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What are Rare Plants
and where did they come from?
Since the first botanical explorers hit the coast of California in 1791, over 6,000 varieties of plants have been identified and named. This is a rich flora, comparable to the number of plant varieties that occur in the U.S. east of the Mississippi. The high diversity of plants in California is due to the amazing range of habitats present in the state. Annual rainfall ranges from near 0 to over 100 inches per year from south to north. The growing season ranges from near 365 days along the coast to about 75 days in the alpine zone of the Sierra Nevada.
Movement of tectonic plates and the associated volcanic activity created islands on land for fresh colonization and species evolution while isolating populations of some other species. Periodic changes in the climate over a period of thousands of years brought invasions of species from the south and north. While some species appear to be genetically stable, the process of species evolution is still clearly ongoing in others.
What makes a species rare may be attributed to a number of different reasons. The complex of habitats as explained above gives rise to very narrow habitat ranges of many species. Often, these species occur in small or concentrated populations covering from a few hundred square feet to a few acres. Most of these species were probably never common and never will be.
Over one third of the species native to California are endemic to the state, that is, they do not grow outside of the state. This compares to one endemic species for Alaska and only five endemic species in New England. A number of other species that are now rare, occupy habitats that are very desirable for urban or agricultural development. They prefer open flat or gradual slopes, sometimes in seasonally wet places. In some cases, these plants may have been very common at one time. In the case of vernal pools (seasonally ponded depressions) they have always been limited in distribution.
Since the first settlers and ranchers arrived here, many plants have invaded the natural landscapes in California. Today, nearly one in three species found in the state were introduced from other continents or even a few have made their way here from the east coast. These species vigorously compete for space against natives, reducing the numbers or completely overrunning populations.
The natural controls that were present in their homeland do not exist here. Finally, a number of animals have been introduced both intentionally and unintentionally replacing native herbivores and consuming native vegetation often to the point of favoring noxious non-native plants.
Protection of rare plant species began in 1977 with the passage of the Native Plant Protection Act. In 1984, the state passed the California Endangered Species Act in recognition of the tremendous threats facing the California Flora. Federal protection of plants began in 1973 with the endangered species act. This act provides protection of endangered species on public lands while state laws provide for some protection on private lands if a project falls under the requirements set forth under the California Environmental Quality Act of 1970. Protection is extended to not only state and federally listed species but also to species that can be shown to meet the criteria for state listing.
The process of listing species both at the state and federal level is often snarled by politics. Only a handful of species have been added to the state list of 216 special status plants since 1992. The California Native Plant Society had to sue the U.S. Fish and Wildlife Service in 1991 to move the listing process onward for over 130 plant species stalled in the department.
Determining which plants need to be listed has been the core of the C.N.P.S. efforts. Since the formation of the society in 1968, this statewide organization, begun by a number of professional and amateur botanists, has developed rare plant lists and challenged botanists of all levels to provide rarity, endangerment and distributional data for numerous native species. The C.N.P.S. "Inventory" is now nearing completion of its 6th edition, which is used by all government agencies and private consulting companies.
The status of each species is reviewed continually to determine if it is rare and/or endangered (List 1B) or of limited distribution (List 4) and in need of monitoring for future upgrading. Some species are simply not familiar enough and require further information (List 3) or are rare in California but more common outside of the state (List 2). The rare plant data collected by field botanists is compiled by the Department of Fish and Game Natural Heritage Program in Sacramento. C.N.P.S. has to date reviewed the status of over 2,000 taxa for its newedition of which at least 90 taxa occur in Napa County.
How much protection does all this effort yield for California plants? Native plants are currently under much greater threat than they have ever been before. Even if we can slow the overwhelming amount of development pressure in the state, we have many issues to solve with invasive exotics, feral animals, overgrazing, road building, lumber cutting, toxic spills, and just plain human error.
(written by Jake Ruygt, botanist)
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