Those who spend time in California hear it described in superlatives: highest and lowest points, greatest number of plant species, greatest number of endemic plant taxa, greatest number of climatic zones, most complex geology, greatest number of endangered species (an unfortunate superlative), and so on. California also contains some of the most diverse and complicated patterning of vegetation of any area of comparable size in North America. Combinations of complex geology, climatic conditions, natural disturbance regimes, and topography, coupled with high plant species diversity, have created an extremely diverse assortment of vegetation types.
Classifiers of California’s vegetation face an urgent task: knowing that many of the lower-elevation landscapes are rare and endangered, and that they are being destroyed rapidly underscores the seriousness of conservation. Only with quantitative vegetation descriptions can we easily distinguish the rare, threatened, or endangered types from the other, more common ones.
As we encounter economic pressures that alter and destroy our vegetation, the amount of time to distinguish its many forms and promote their protection appears frighteningly short. California is full of examples of rare vegetation types, such as old-growth redwood, giant sequoia, Monterey cypress, or Torrey pine groves. Although many people know and revere important natural assets in the state, others are less well known but of equal importance. Most of the state’s 11 species of cypress (Callitropsis and Hesperocyparis) form stands of vegetation and are naturally rare. More than 20 of the state’s 60 manzanita species are naturally restricted to specific areas as endemics, but they appear abundant enough to form their own rare vegetation stands. The CNDDB determined that 135 out of the 280 vegetation types listed in the Holland (1986) classification are rare enough to warrant concern and some level of protection. Further, at least 50 types have less than 800 hectares of high-quality habitat.
We are at a crossroads. The federal and state Endangered Species acts are undergoing more scrutiny and challenge than ever before. The legal tools for conservation of biodiversity are not always explicit when it comes to conservation of vegetation types and ecosystems in the state. We find vague inferences and intent language that address conservation of habitats and ecosystems in the CEQA legislation (Wagner 2006).
Conservationists recognize that to sustain the natural values of California, we must have something more useful and comprehensive than single-species-based conservation. CNPS intends eventually to secure explicit legislative protection for rare and endangered vegetation types; however, we currently recognize the need to support their existence and to justify their protection through existing mechanisms. These include CEQA, NEPA, and a number of innovative programs.
Recently, conservation programs based on vegetation have begun. These include both state and federal regional conservation planning efforts, the Natural Community Conservation Planning (NCCP) and Habitat Conservation Planning (HCP) programs. A pilot project initiated by the state’s 1991 NCCP act for southern California’s coastal sage scrub, and other multispecies conservation plans, were followed by studies in the Coachella Valley, Sacramento Valley, San Joaquin Valley, western Mojave Desert, and other areas. Further, we can support protection for vegetation through identifying environmentally sensitive habitat areas per the California Coastal Act, and through seeking their recognition for conservation in county general plans.
Conceptually, the HCP and NCCP programs that are grounded in the best available information and mapping of vegetation/habitats best protect a suite of natural communities in which rare species occur. These programs have an advantage of establishing habitat reserves for key portions of an ecological region, while allowing areas of lesser ecological importance to be modified or developed, satisfying both the conservationists and developers. However, lack of scientific information and implementation has compromised these programs. They have, by default, focused on individual threatened or endangered indicator species within broadly conceived ecosystems. Chief among the reasons for this compromise is insufficient information about critical habitats for many species, coarse-level vegetation mapping of these areas, and insufficient funds for establishing and maintaining preserves. CNPS believes that, upon developing quantitative vegetation descriptions and maps, we can better define critical habitats for numerous targeted rare species (Evens and Klein 2006) and better target conservation and management efforts.
As an example, not all areas within the zone described for NCCP activities are prime habitat for the California gnatcatcher, the bird species motivating much of the conservation work in southern California. Classification of vegetation can play an important role in resolving conflicts. Broad conceptual views of coastal sage scrub and chaparral in the vein of the Munz and Keck (Munz 1949, 1959, Munz and Keck 1950) or Holland (1986) classification systems may under- or overestimate the value of areas as gnatcatcher habitat. From detailed observations by ornithologists, we now know that the bird responds to distinct mixes of plant species’ composition within a special structure (Read 1994, White 1994d, RCIP 2003). Only a detailed, quantitatively based vegetation classification and map can specify such important resource differences.
Using carefully crafted quantitative vegetation descriptions can aid multispecies conservation. There are, however, vegetation types that are in and of themselves rare. These may occur within areas not slated for broad-scale habitat planning, and they may exist without containing a single threatened or endangered species, such as California sycamore and valley oak riparian woodlands. Yet, we recognize the uniqueness of these vegetation types and the threats to their existence. If we want to develop a framework for the protection of these types, we need to develop defensible definitions for them.
The different categories of rare vegetation surpass the natural forms of rarity of individual species: (1) rare species can form rare vegetation types; (2) common species are only rare in a particular stage of vegetation development (e.g., old-growth forest or old-growth chaparral); (3) common types have been reduced by human activities; and (4) unusual assemblages of otherwise common species (e.g., geographic mixing zones where desert species blend with coastal species, or where northern species mix with southern species) can be rare. All cases are important markers of biodiversity, global climate change, and shifting conditions.
The conservation-based Holland classification formerly used by the CNDDB has been useful in defining and prioritizing many rare habitats. However, it is insufficient in representing all the different rare types, and in answering repeated questions about the similarity of many vegetation types, because of the lack of quantitative data. Does southern maritime chaparral differ significantly from adjacent chamise chaparral or southern mixed chaparral? How can we differentiate sycamore alluvial woodland from southern sycamore-alder riparian woodland? Such questions arise because the CNDDB has identified only some vegetation types as rare and endangered. Therefore, landowners and resource managers want to know how to identify and protect the rare types, or how to demonstrate or discredit the uniqueness of other vegetation types. Rigorous definitions and mapping have been problematic because only recently have funding efforts been dedicated to quantifying salient components of these types across broad regions.
We treated Holland high-priority communities in various ways in the first edition, including translating habitats into alliances or associations when we could. The following lists identify some of Holland “rare communities” that still need precise sampling, even after more than a decade of work.
The enormous task of classifying vegetation multiplies several times when we consider classifying the vegetation of the entire country. Yet, an integrated and complete classification of vegetation for the nation affords us the most comprehensive approach to conservation and management of our nation’s natural ecosystems. Conservationists and ecologists have long recognized the need for a national classification. Efforts have proceeded in two ways: from the top down and from the bottom up, in the form of small, regional systems pieced together to form a yet incomplete, fine-scale national classification.
Work on refining the National Vegetation Classification has been ongoing and includes a number of new vegetation surveys, a new refinement of the vegetation hierarchy (Faber-Langendoen et al. 2007), and efforts to maintain and ratify the best and most recent vegetation assessments. In 1994 Michael Barbour chaired a special subcommittee on vegetation classification on behalf of ESA. Its principal charge was to develop a united system for use in the nation (Barbour 1994c). Since then, this committee has been working on standardized rules for field data collection and description of vegetation and has developed a ratification process to induct new vegetation types into the National Vegetation Classification (Jennings et al. 2008). Links between NatureServe, the Federal Geographic Data Committee, and the ESA Vegetation Panel assure that new information becomes part of the standardized National Vegetation Classification. For those interested in the full classification and in investigating any of the 1,200 nationally recognized alliances and 6,000 associations, go to the NatureServe Explorer website: http://www.natureserve.org/explorer/.
Now conservation and resource managers are speaking the same language. Having specificity is important in both a practical manager’s and an idealistic conservationist’s lexicon. Quantitative work that the U.S. Forest Service, other land management agencies, and CNPS have done to attain this level of understanding is of direct value to conservation in the state.
Since the publication of the first edition of this book, CNPS has made a serious commitment to collecting data, educating the public, and distributing information about vegetation. In 1999 it created the first staffed position in its Vegetation Program. Currently, the program consists of a senior lead ecologist, three associate ecologists, and ten seasonal ecologists, who collect data in specifically defined areas of the state agreed upon as high priority for conservation. The Vegetation Program is represented as part of the state’s Biodiversity Council Vegetation Working Group, and is a signatory to the state’s Memorandum of Understanding of Vegetation Classification and Mapping (http://biodiversity.ca.gov/vegmou.html). The Vegetation Program is an integral piece of the multifaceted strategies for native plant conservation by CNPS. Over the past decade, we have been most successful in developing detailed, quantitative vegetation classifications of various high-priority areas of the state, such as the central coast, Sierra Nevada foothills, portions of San Diego County, and western Riverside County. Other long-term goals include the development of rare vegetation and grassland initiatives.
We are now refocusing on rarity as a factor in vegetation conservation following several years of regional assessment. Currently, the Vegetation Program has plans to identify a rare vegetation coordinator to work with CNPS chapters and other partner organizations, to identify locally or regionally important rare vegetation, and to work systematically to inventory, describe, and protect these types.
In addition to refining of the classification, we must refine our concepts of threat and endangerment—and of the different levels of biodiversity—as they apply to vegetation, so we can best represent and protect rare vegetation. As we define more alliances and associations, we expect to identify an enormous number of rare vegetation types. How can we justify protecting all of them in a political, social, and economic climate where it is becoming nearly impossible even to legally “list” and protect strongly substantiated rare species? Can we effectively justify supporting legal protection for potentially hundreds of rare assemblages of plants? Two points may serve as examples of the complexity of the issues involved.
We already know that several quantitatively defined associations of Quercus douglasii alliance in the southern Coast Ranges are restricted to just a few sites of limited acreage (Borchert et al. 1993). However, they have no rare species associated with them. Instead, they are uncommon assemblages of widespread species limited by topographic position and soil type. Are these limited assemblages as important as plant associations containing a mixture of rare species that occur nowhere else? To evaluate other situations, do we incorporate wildlife values, watershed protection values, and other non-vegetation traits into our assessment and deliberations? We assume that conservation would consider these things, and we can use detailed descriptions and analyses to assist in answering these questions.
Secondly, because of direct human disturbances, including livestock grazing, agricultural land conversions, and invasion by non-native plants, excellent examples of common vegetation types are becoming rare in themselves. Should we not become interested in identifying and quantifying the best remaining examples of some of our more common plant assemblages as well as the rare ones? Ranking and prioritizing sites based directly on human and unnatural disturbances underscores another need for quantitative assessment that goes beyond standard vegetation sampling techniques.
Conservation strategies surely will arise that we do not fully comprehend at this time. They may enable us to view more clearly the value of individual vegetation alliances or associations in terms of larger watersheds and landscapes. We envision sustaining a sequence of states in the vegetation and patchwork of ecosystems that will enable us to foster the natural processes necessary to maintain biodiversity with or without legal protection for any specific plant alliances or associations. In the interim, we can commit ourselves to analysis and study of vegetation so we can provide some of the scientific building blocks for these larger goals.
CNPS and other organizations recognize the continued need to identify and protect all vegetation types as units of biodiversity in themselves. We also recognize that recent conversion and degradation of vegetation types have disrupted the integrity of the ecological functions of our natural environments, leading to losses of sensitive plant and animal species and decreases in biodiversity. As done by the Natural Heritage network of NatureServe, and originally by the Nature Conservancy, we will continue to use natural communities as a “coarse filter” in combination with rare species to assess ecological health, identify land management risks, and assess future conservation priorities. Methods that CNPS has developed recently in conjunction with other partners to consistently sample, classify, map, and monitor vegetation within an integrated approach give us powerful tools to conserve and manage our state’s precious natural vegetation resources.