Ecological Restoration of Coastal Sage Scrub andIts Potential Role in Habitat Conservation PlansPETER A. BOWLERDepartment of Ecology and Evolutionary BiologyUniversity of California, IrvineIrvine, California 92697-2525, USA andWhite Mountain Research Station3000 E. Line StreetBishop, California 93514, USA

ABSTRACT / Extensive acreage loss of coastal sage scrub(CSS), isolation of surviving stands, and the federal listing ofseveral animal species with obligate relationships to this plantcommunity, particularly the threatened California gnatcatcher(Polioptila californica), have led to attempts to create CSS tomitigate habitat lost to urban development and other causes.Many of these creations lie within habitat conservation plan(HCP) sites, and they could play a more prominent role by be-ing repositories for plants taken from a single site having site-specific genetics.

Among others, one technique that increases initial resem-blance to natural stands uses digitized, to-scale photography,which has been ground-truthed to verify vascular plant associ-ations, which appear as mosaics on a landscape. A combina-tion of placing patches of salvaged, mature canopy plantswithin larger matrices of imprinted or container plant plots ap-pears to significantly enhance immediate use by CSS obligate

bird species, accelerate “spread” or expansion of CSS, andcan also introduce many epiphytic taxa that otherwise wouldbe slow or unable to occupy developing CSS creations. Rep-tile, amphibian, butterfly, and rodent diversity in a salvagedcanopy restoration case study at the University of California,Irvine, showed CSS species foraging and inhabiting trans-planted canopy patches.

Using restoration techniques to expand existing CSSstands has more promise than creating isolated patches,and the creation of canopies resembling CSS mid-fire cyclestands is now common. Gnatcatchers and other birds userestorations for foraging and occasional nesting, and insome cases created stands along “biological corridors” ap-pear to be useful to bird movement. Patches of trans-planted sage scrub shrubs along habitat edges appear tobreak up linear edge effects. There are no data on whichlong-term survival, succession, or postfire behavior can bepredicted for CSS restoration sites, and postfire communitychanges are not part of either mitigation or restoration plan-ning at present. Long-term planning including burning isneeded so that a fire-adapted habitat will develop. Restora-tion is important in retaining genetic resources, for amelio-rating edge effects, as habitat extenders in buffer zonesaround HCP sites, and by providing areas into which natu-ral stands can expand.

Coastal sage scrub (CSS) restoration faces regionallandscape problems, including the deposition of air-borne nitrogen from anthropogenic sources (Allen1997), foliar damage from air pollution (Westman1985), lack of species richness (Davis 1999), increasingweediness of natural stands (Westman 1987, Bowler1990a), large seed banks of exotics, a lack of mycorrhi-zal fungi at restoration sites, and the inherent difficultyof establishing many species outside natural stands.Lack of understory annuals as compared with nearneighbor stands (Bowler 1999b) and a lack of demon-strated fire cycle behavior (Bowler 1999a; see Figs. 1–3)are problems linked with mitigation and restoration.

The term “coastal sage scrub” is a generic one, like“montane forest.” Since Westman (1981a, 1981b) de-fined four major vascular plant associations in coastal

sage scrub (Diegan, Riversidian, Venturan, and Dia-blan) and two in the closely related coastal succulentscrub in northern Baja California, Mexico (Westman1983; see DeSimone and Burk 1992 for a review of CSSassociations), nearly a dozen subassociations have beenrecognized (Kirkpatrick and Hutchinson 1977, 1980,Jones and Stokes 1992); however, few attempts havebeen made to restore these finer-grained groupings.The finer-grained aspects of this complex community,including its subassociation and exposure differences,should be recognized in conservation (DeSimone andBurk 1992) and restoration planning (Read 1994).Habitat conservation plan settings provide excellentopportunities for this.

Coastal Sage Scrub

Coastal sage scrub once covered perhaps 2.5% of thecoastal lowlands in California and extended along Pa-

KEY WORDS: Habitat conservation plan; Ecological restoration; Coastalsage scrub; Mitigation; Plant salvage

DOI: 10.1007/s002670010064

Environmental Management Vol. 26, Supplement 1, pp. S85–S96 © 2000 Springer-Verlag New York Inc.

cific coastal Baja California, but today is highly frag-mented in California, with most fragments having adominance of edge, frequently in direct contact withurban development or roads (see Saunders and others1991 for a review of the consequences of habitat frag-mentation). In a sense this is also a “lack of edge,”because natural “edges” abut oak woodland, grassland,or chaparral. Prior to the 1970s CSS was a poorly un-derstood community, in part because some of the dom-inant canopy plants can invade burned stands of chap-arral for a few years, thus it was viewed as successional(see DeSimone and Burk 1992 for an excellent litera-ture review). In the early 1980s Westman (1981a–c,1883, 1985) published a series of studies demonstratingthat CSS is a distinct community, and there has beenextensive research on it since then.

Sage scrub exhibits a postfire cycle of species appear-ance and replacement, beginning with characteristi-cally fire-following taxa, such as Lupinus, Phacelia,Escholtzia and Amsinkia spp., and perennials, such as

Leymus condensatus and Malacothamnus. Both annualsand understory perennials persist perhaps 7 years fol-lowing a fire. Some of the species, particularly fire-followers, are present in the seed bank, whereas othersinvade from adjacent unburned stands and from theregional seed rain. The shrubs regenerate through rootsprouting, and a gradual accretion of nonfire-followingherbaceous taxa occurs until about 17–20 years, afterwhich understory species richness declines. At about 40years after a fire, there are few remaining.

Fire suppression has generated large fuel loads pro-ducing vast burns. Prior to this, canopies had many ageclasses for each species (Fig. 1). This cycle of postfirediversity (Fig. 2) and its emulation has not been incor-porated into restoration plans, which instead attemptto mimic mid– or late–fire cycle conditions. Example ofCSS restoration strategies that do emulate the fire cycleare presented in Fig. 3.

Most stands today are surrounded by grassland dom-inated by annual European grasses or the exotic black

Figure 1. An idealized representation of postfire succession in coastal sage scrub, illustrating interburn cycles of 201 years.Following fires of this frequency, there is a burst of species richness as fire-following taxa appear immediately after a burn, thendecline at around 7 years, with shrubs recovering rapidly and an accretion of non-fire-following annuals present until around17–20 years. After burning, the cycle begins again.

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mustard (Brassica nigra). Native grassland is nearly com-pletely extirpated and southern oak woodland is a re-stricted, endangered habitat. Altered fire cycles, lack ofadjacent stands of different age classes, and isolationfrom “regional seed rain” has led to decline in diversitythroughout the postfire cycle. Late successional epi-phytic species, such as lichens, have suffered extensivelosses with many regional extinctions (Bowler and Rief-ner 1999). As a result, over 60 vascular plant and over30 animal taxa in CSS are viewed as rare, threatened, orendangered. In the face of the magnitude of habitatloss and extent of decline of plant and animal specieswith obligate relationships to CSS, regional preservesystems (the Natural Communities Conservation Plan,or NCCP, for example) have been designed in an at-tempt to protect surviving large blocks of habitat whileresolving political conflicts. The trade-off of preservingsome areas and exempting rare, threatened, and en-dangered species from legal protection was adopted bystate and federal agencies, as well as the developers whowere largely its promoters and architects. Under these

agreements, if additional species qualify for ESA pro-tection, the areas to be developed would remain ex-empt (“no surprises”; see Smallwood and others 1999).Preserving designated blocks of habitat does not neces-sarily benefit all the sensitive species within them, asmany species have widely ranging, often coastal distri-butions so that single blocks reflect little of the genet-ics, remaining populations, or actual distribution ofsuch taxa (Westman 1987). Conservation plans, such asthe NCCP and habitat conservation plans (HCPs), havebeen widely criticized in both the environmental activ-ist (Luoma 1998, for example) and academic commu-nities (Shilling 1997).

Mitigation

Although some papers published as early as 1990(Bowler 1990b) recommended no further sacrifice ofCSS, compensatory mitigation was not required untilthe California gnatcatcher was federally listed as athreatened species in 1993. Around 1996, mitigation

Figure 2. An idealized representation of postfire succession in an unburned condition beyond 40 years. In this situation, afterfire a similar postfire succession begins, with understory taxa declining after about 17–20 years, eventually being nearly absentby 40 years after the previous fire.

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became required for taking CSS not currently sustain-ing gnatcatchers. One of the first gnatcatcher and CSSmitigations was voluntary, when in 1989 the Universityof California, Irvine, agreed to replace CSS habitat lostto university development and to place a 46-m bufferzone between new development and the university’sEcological Preserve, which supports six to eight pairs ofgnatcatchers (Atwood and others 1998). Because com-pensatory mitigation is usually driven by the Endan-gered Species Act, habitat creation projects focus onshrubs known to be used by listed animal species. CSS

created to mitigate gnatcatcher habitat loss usually in-cludes such shrub species as buckwheat (Eriogonum fas-ciculatum), coastal sagebrush (Artemisia californica),black sage (Salvia mellifera), and California encelia(Encelia californica).

The approach of “replacing” habitat loss using asingle formula has led to diminished habitat diversity.The replacement rarely reflects the aspect, exposure,structure or floristic quality, or successional trajectoriesof the habitat taken. CSS sites created under mitigationrequirements make little attempt to restore the whole

Figure 3. Examples of restoration strategies designed to emulate postfire succession in coastal sage scrub.

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community; rather, they are simply canopy projects.Though they may emulate a mid– to late–fire cyclehabitat, they are species poor in the understory.

For CSS the U.S. Fish and Wildlife Service usuallyrequires a mitigation ratio of 2 acres created: 1 acrelost. Natural habitat is ranked as low, intermediate, orhigh in value. High value indicates occupation by gnat-catchers or that the site of loss is contiguous with otherCSS habitat. Frequently one acre is required to bereplaced in kind, but the other might be a “set aside”(preserved) or some other activity such as eliminationof exotics like cardoon (Cynara cardunculus). The goalis usually to have met specified standards within a 5-yeartimeframe, with performance completion expected tobe 20% the first year, 40% the second, 50% the third,65% the fourth, and a minimum of 80% by the fifth.Goals usually include cover and diversity (i.e., survivalof the plantings), for example, 15 native species have acombined cover of 80% in 5 years. Between 3000 and5000 acres of CSS loss are being mitigated in this man-ner in Orange and San Diego Counties (Fred Robertspersonal communication).

CSS restoration, as practiced for mitigation, is anassembly rather than a successional process. Tech-niques commonly used in creating CSS habitat includeimprinting (mechanically forcing seeds and mycorrhi-zal fungi into the ground), hydroseeding, broadcastseeding by hand, and installing container plants grownin nurseries. The translocation of rescued or salvagedplants is also gaining acceptance. Some sites selectedfor the projects likely could never sustain most of thespecies in nearby CSS stands because they are locatedon graded road margins (“biological corridors” becausenew freeways usually pass through open space areas,thus roadway burrow pits are the only links betweenurban isolated natural areas), on closed and cappedlandfills, abandoned agricultural fields, and at othersites disturbed by heavy equipment.

Finally, mitigation responsibilities are usually linkedto 5-year performance criteria based on shrub densities,not species richness. Once these criteria are met fund-ing and maintenance are terminated. The result isoften an aberrant “community” with a strange mixtureof species, such as the dominance of an Atriplex speciesnot occurring in natural CSS.

Although not widely discussed, most designs arebased on mid– to late–fire cycle vascular plant species(those present at mid–fire cycle times, rather than theentire assemblage present above ground and in the soilseed bank). Mimicking mid–fire cycle above-groundplant assemblages could still allow burning after per-haps a decade, then the introduction of fire-followingtaxa and other understory taxa as suggested in Fig. 3

(Bowler 1999b). Producing CSS “canopy projects” isnow routine, but these created habitats are not fol-lowed up with understory supplementation. Regretta-bly, burning and understory supplementation are notpresently part of mitigation or restoration plans, and tomy knowledge there has been no scientifically con-ducted and measured burn of created CSS with recov-ery and subsequent succession examined. Thus, CSSrestoration is still in its infancy.

Canopy projects resemble natural stands in summerwhen the annual understory is absent, but created CSSadjacent natural stands may eventually support morespecies. Canopy projects may be all that can be hopedfor along freeways and roadsides, which are often “bi-ological corridors” that link isolated CSS stands.Patches of canopy plants also soften edges and expandgnatcatcher territories. HCP sites could serve as geneticrepositories for plant patches transplanted from nearbysites destined for destruction. This would both enhanceonsite habitat and preserve external genetic resources,which otherwise would be lost.

Some of the pitfalls of a mitigation based approachinclude:

● Five-year timelines are insufficient for CSS restora-tion because the inter-fire cycle within this commu-nity is decades long.

● Some projects create strange assemblages of spe-cies, such as the dominance of Brewer’s saltbush(Atriplex lentiformis (Torr.) Wats. ssp. breweri (Wats.)Hall & Clem.) at Crystal Cove State Park (OrangeCounty, California).

● Overhead sprinkling causes aberrant, spindly, andunbranched growth forms. Plants can have de-formed, nonseasonal foliar characteristics, oftenwith dolichoblast and brachyioblast leaves simulta-neously in the late summer. Overhead sprinklingenhances nitrogen supplies, encouraging such ex-otics as annual grasses and black mustard, especiallyif reclaimed water is used.

● Many shrub and subshrub species have stuntedgrowth forms, particularly on landfills or alonggraded road margins, due in part to overhead sprin-kling and to the density of seeding.

● Some mitigation projects are poorly sited. CSS mit-igation sites often suit the convenience and eco-nomics of the developer or highway project, ratherthan the ecological need. Often the aspect, slope,and edaphic factors are not matched to the speciesplanted within created habitats.

● Many mitigation projects are never actually imple-mented, and within those that are, there is often

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poor follow-up and the protocols for monitoringare inadequate.

Standard and Historical Approaches to CoastalSage Scrub Restoration

In the early years of CSS mitigation, standard pal-ettes of shrub species with a few understory plants wereconsidered adequate to meet compensatory mitigationgoals. Nursery-grown container plants were used incombination with hydraulic (“hydroseeding”) or im-printed seeding. Usually 1-gal container plants thathave been inoculated with mycorrhizae are planted.Although this is still the most significant way sage scrubrestorations are implemented, there is an increasingconcern and requirement for near-neighbor or onsiteseed sources.

The most widely used landscaping technique is thatof hydroseeding, in which native plant seeds are mixedwith water, often certain fertilizers in low concentra-tion, and a mulch-like substance, which is then sprayedonto the restoration site. This approach reduces ero-sion on a short-term basis, but it can initiate germina-tion prior to application, causing rapid mortality; theseeds may fail to contact the soil; or they may produce

a random occurrence of plants rather the kinds ofassociations seen in wild stands, and so forth.

Selection of a Model on Which to Base RestorationDesign

To emulate natural habitat for CSS, a model siteshould be selected with exposure, soil, and slope similarto the restoration site. The natural site can then becharacterized using transects, quadrats, and digital pho-tography—and both the model site and the restorationshould then be monitored to form an ecological basisfor performance standards and to allow for correctionsas the site develops. On the University of California,Irvine (UCI), campus in a linear Natural CommunitiesConservation Plan (NCCP) “biological corridor” adja-cent a freeway, an experiment was undertaken usingdigitized aerial photography of the model site, whichwas then ground-truthed by transects (Bowler and De-merjian 1996). The mosaic pattern of plant assem-blages within the larger model community whichemerged was then used as the actual, to-scale design forthe restoration (Fig. 4). This was very effective in en-hancing the ecological resemblance to the model site.Within a year after planting, gnatcatchers were usingthe corridor extensively, although primarily as a pas-

Figure 4. A mosaic representation of coastal sage scrub plant assemblages developed from digitized aerial photographs andtransects. This design was incorporated into a repeating sequence used to produce planting designs that directly emulate themodel mimicked in a coastal sage scrub restoration at the University of California, Irvine, based on Bowler and Demerjian (1996).In this figure the computer-delineated, wallpaper-like pattern of coastal sage scrub canopy (polygons) are lain on a 100-square-foot grid. (Reproduced with permission from Restoration and Management Notes.)

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sage rather than resident site. The use of an actualecosystem model for design and planting achieves eco-logical similarity more rapidly than hydroseeding.

Onsite and Near Neighbor Collection of Seeds andCuttings

Under ideal conditions, a donor habitat, which willbe destroyed, can be identified several years in advanceof its destruction and can be viewed as a farm. Forexample, Bowler (1999b) collected seed from 38 nativespecies at Crystal Cove State Park over several years foruse in onsite restoration. In a well-executed alluvialscrub restoration, seed from 24 species was collectedfor the project beginning 2 years before implementa-tion, which allowed purity, germination, and seed con-tent to be analyzed (Blane 1992). At UCI, seeds arecollected, plants moved, and soil (if available) is ulti-mately saved and transported to on-campus restorationareas in advance of development over a period of years.A nearby protected site with similar soil type and depth,slope, and exposure can be dedicated as a host site, withonly material from the donor site planted there (muchlike a genetic voucher site).

If it is not possible to conduct onsite seed and cut-tings, a nearby neighbor site should be selected (Bowler1999a). The importance of retaining local genetics isbecoming increasingly recognized among restoration-ists in California and is now routinely required by reg-ulatory agencies. Using HCPs as designated recipientsof site-specific salvage material would both significantlyincrease the value of mitigation conducted in them aswell provide added protection for resources otherwisesacrificed.

One of the problems of early mitigation sites is theirextensive introduction of seeds from distant parts of aplant’s distribution (Bowler 1999a). Non-native speciesalso tend to follow mitigation projects because of thedisturbed habitat and also because of irrigation used toestablish plants. As an example, the Argentine ant isable to rapidly expand its distribution following waterused for landscaping. This aggressive species immedi-ately displaces native ant species (Fisher and Case per-sonal communication). Ant-eating species, such as thesensitive and rare San Diego horned lizard, are thusaffected, not only because their food base is eliminatedbut also because Argentine ants “swarm” their preda-tors. The community’s food chain is exacerbated by thepractice of aligning freeways through open-space areas,which otherwise would have strong core areas withoutthe suite of exotics that use roadside habitats as aconduit for colonization.

Salvage of Seed, Plants, and Soil from“Doomed” Sites

It should be emphasized that transplantation shouldonly be employed as a rescue and recovery techniqueon “doomed” stands and should not be an avenue tostrip wild stands in preserves of their recruitment; nor,clearly, should it be viewed as an easy means of simply“moving” a habitat from one site to another so thatdevelopment can occur in a preferred site.

Values for donor and host CSS transplantation sitesinclude:

● As seed sources—collection can be intensively pur-sued for years before their elimination: over a 4-yearperiod approximately 450 lbs of seed were collectedfrom a small on-campus site

● Sources for recruitment plants, or seedling collec-tion—transplants are mycorrhizal from naturalstand association (site-specific inoculum); over thepast 4 years over 1000 seedlings and second-tierplants were collected from on-campus sites

● Sources for mature, canopy forming adults—whichbring epiphytes (lichens, algae), invertebrates, andso forth when transplanted

● Genetic integrity—seed, seedlings, and adult plantsare from a single locality

● Soil—bringing with it mycorrhizae and the crypto-zoic community

● These sites can be farmed; “doomed” stands arepossible sites into which seed can introduced, evenwatered, to generate recruitment plants that aremycorrhizal in the wild

Restoration host sites values:

● Seed sources—exceptional seed production usuallyoccurs when canopy plants are transplanted, whichcan be harvested or left to further seeding of arestoration site

● Sources of seedlings—extraordinary self-seeding re-sults in large numbers of recruitment plants, whichcan be harvested because they diminish in numberin any event due to competition for water, light, andspace

● “Instant habitat” attraction/effect for birds, mam-mals, and invertebrates that use canopy habitatswhen transplanted

● Wild-grown canopy plants jump-start restorations

Salvage of CSS was historically viewed as difficult withlittle likelihood of survival. Developers readily acceptednursery-grown container plants and hydroseeding be-

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cause planting and application could be timed to devel-opment and costs could be accurately estimated. Becausesalvage was not required by agencies, the feasibility of thistechnique in CSS was only recently studied (Bowler andothers 1994, Bowler 1999c). Although an excellent andpromising means of recovering plant material of knowngenetics, salvage is still experimental.

Transplantation of recruitment seedlings from nat-ural stands has a very high success rate (see Table 1),and the plants are mycorrhizal by the time they are afew centimeters in height (Bowler and others 1994).Either direct transplantation can be employed for seed-lings, or, if the soil is dry and the weather hot, they canbe held in a greenhouse for a few weeks to reducetransplantation shock and increase survival (Bowlerand others 1994). In other studies, Bowler (1999c)demonstrated that second-year and large older plantscan also be transplanted. Moving plants from sites be-fore development is now an accepted practice imple-mented by the Nature Conservancy in its managementof the Nature Reserve of Orange County (NCCP landswithin Orange County), and large canopy plants can betransplanted for less than $4 each, compared with com-mercially available gallon container material at ,$3(Bowler 1999c). Salvage can be done with hand laboror heavy equipment. Salvage plants of all sizes shouldbe undertaken during winter (November through mid-March) when winter foliage is apparent in seasonallydimorphic taxa. Winter precipitation is usually suffi-cient to establish plants, so that if transplanted withinthe winter rain period, irrigation is not required. Fac-ultatively deciduous species transplant most success-fully, probably because they can lose their leaves inresponse to transplantation shock, then recover andregrow leaves. Nondeciduous species have higher mor-tality rates.

Root Structure

Root structure affects salvage potential. Shrubs withshallow, fluffy roots, such as Artemisia and Salvia, trans-

plant easily, whereas species with a large taproot, suchas Lotus scoparius, are most effectively transplanted fromthe wild as small recruitment plants; mature plants havepoor survival. Nondeciduous species, such as lemon-adeberry (Rhus integrifolia), have poor transplantationsuccess as larger plants. Similarly, toyon (Heteromelesarbutifolia) is difficult to transplant as large individuals.E. californica is an intermediate species, with roots thatcan be shallow and fluffy or more rope-like if in a rockysubstrate. This species can lose its leaves during trans-plantation and then recover. Buckwheat, a nondecidu-ous species with ropy roots, is difficult to relocate. Areview of the root structure of chaparral taxa, includingmany CSS species, is presented by Kummerow andothers (1977; see also DeSouza and others 1986).

In mechanically moved large clumps, a number ofbranches will die, but a few survive and set seed. Re-taining dead plants is important in patch dynamics.The dead plants are used extensively by birds, includinggnatcatchers, and dead or long-dormant plants arecommon in many natural stands.

Grafting

My group has made extensive attempts to graft dis-tinct genotypes of around a dozen CSS shrub speciesonto an individual plant of the same species. This ex-periment was not successful, in that grafted woodyplants are extremely fragile and unsuited to survival inthe wild. Also, deer appear to find the grafting sealantextremely palatable. Santa Ana winds consistently dam-aged grafts. Grafting is not suited to natural-settingrestorations in coastal southern California. It had beenhypothesized that a broad genetic representation couldbe expressed within a restoration site by having individ-ual plants host many genotypes and produce geneti-cally diverse seeds. This did not appear feasible innonprotected settings. Although an interesting con-cept, grafting does not appear to be a viable techniquefor woody plants.

Grafting is effective, however, in the Cactaceae(Bowler and others 1999) and can extend the expanseof such species as Opuntia littoralis and O. prolifera. Inboth of these species, blades can be grafted to createpotential nest sites. This is significant for the coastalcactus wren, which lost 40,000 acres of habitat andaround a quarter of the entire known population dur-ing the 1993 Laguna Beach fires. Cactus nest habitatcan also be expanded by severing large plants at thebase, allowing them to callous. The stubs are thenplanted and reinforced with rebar if needed. Individualplants of O. prolifera 180 cm in height were successfully“transplanted” in this manner; they subsequently flow-

Table 1 Examples of canopy plant (shrub) survival forplants after 1 year

N%

mortality Facultatively deciduous Root type

109 1 Artemisia californica Shallow125 6 Artemisia californica Shallow20 35 Salvia mellifera Shallow? 59 Eriogonum fasiculatum Intermediate;

ropy22 14 Isocoma menziesii Shallow99 81 Lotus scoparius Deep taproot

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ered and set seed 2 years later. Such plantings represent7 years of growth in terms of cladode production andstructure.

Exotics

Because restoration is conducted in disturbed land-scapes, invasive weeds challenge most restoration at-tempts. As an example, CSS and grassland habitats inthe University of California, Irvine, Ecological Preserve(Orange County, California) have about 167 vascularplant species, 31% of which are non-native. Westmanreported a similar ratio for Riversidian scrub, andBowler (1990a) found that most San Joaquin Hills CSSsites were about a third exotic in species composition.Because most (78.8%) of the exotics are annuals in theUCI Preserve, the annual/nonannual ratio shifted from1.13 in the native assemblage to 1.56. The annual/nonannual ratio for the 52 exotics only is 3.7. Exoticannuals dominate the cover of most of the 60-acrepreserve. Exotic grasses appear to retard the expansionof native shrub stand expansion (Allen 1997). Theheavy seed rain of exotic annuals likely alters popula-tion dynamics within the granivorous food chain.

Use of Restoration Sites by Animals

Habitat conversion, including attempting to alterexotic dominated habitats and return them to a nativevegetation condition, changes animal use and pres-ence. At a CSS creation site in the San Joaquin MarshReserve, which had been closed canopy artichoke,ground squirrels left after a successful restoration wasin place. Because of the open ground area betweenpatches or plantings in restoration sites, there are nu-merous ground-feeding birds present that are excludedby the thatch of dead annual grasses. As restorations areinstalled in formerly artichoke or exotic grassland hab-itat, California gnatcatchers use canopy CSS standswithin a few days of installation. Bird point counts atthe UCI Ecological Preserve indicate that 13 speciesconsistently use the restoration plots, and at adjacentCSS control sites between 3 and 10 species are found.

Similarly, all of the four species of lizards present inthe natural stands sage scrub, Elgaria multicarinatus,Eumeces skintonianus, Sceloporous occidentalis, and Utastansburiana, were present in restoration sites at theUCI Ecological Preserve. Three species of snakes, Lam-propeltis getulus, Masticophis flagellum, and Pituophis mela-noleucas, were also observed in the restoration sites. Theonly species absent from the restoration plots was thering-necked snake (found once in the natural standcontrol sites). The discussion of vertebrate use of the

UCI Ecological Preserve is based in part on unpub-lished data by Fisher and Case (used with permission).

Converting a disturbed habitat from artichoke andmustard can change the mollusk fauna it supports. Forexample, the exotic snail Helix aspersa no longer usedsuch an area after conversion to CSS, and the site wascolonized by Helminthoglypta tudiculata (a native landsnail associated with CSS in adjacent natural stands). Atanother restoration site, the exotic predatory decollatesnail was present when the site was closed canopy arti-choke, but is now absent from the site, which is restoredCSS. This is suggestive that at least native land snailsmay track and prefer CSS to the environments createdby European grasses, mustard, and artichoke.

Eighteen species of butterflies are known from theUCI Ecological Preserve and the urban dwelling areaon its eastern edge. Eleven species have been recordedin CSS over the past 6 years, and five of these speciesand two others (not previously noted at the site) occurin the CSS restoration (Bowler 1999c).

As Zedler (1998) has shown for salt marshes, evenseemingly “simple” communities are difficult to rees-tablish in ecologically functional ways. At this pointmid–fire cycle canopy project creation is well under-stood, and many of them are used by wildlife such asbirds, butterflies, and small mammals.

The highly fragmented UCI Ecological Preserve sup-ported eight focal pairs of gnatcatchers in 1997, six in1998, and seven in 1999 with birds extensively using tworestoration sites (mostly salvaged canopy plants; Atwoodand others 1998). Extensive use by butterflies, birds (in-cluding cactus wrens and gnatcatchers), and reptiles sug-gests that tight (10-m diameter), closed canopy andpatches of large, transplanted canopy shrubs attract andare used immediately by most of the native fauna.

Biological Corridors

In a review paper (Beier and Loe 1992) and a subse-quent study (Beier and Noss 1998), habitat corridors (dis-persal corridors and landscape linkages) were character-ized by five primary functions: wide-ranging animals cantravel, migrate, and meet mates; plants can propagate;genetic interchange can occur; populations can move inresponse to environmental changes and natural disasters;and individuals can recolonize habitats from which pop-ulations have been locally extirpated. Succession, particu-larly epiphytic succession (lichens, algae, and fungi),should also be able to occur within such corridors. Aprimary concern is whether restorations and mitigativehabitat creations are sinks, drawing animals into habitatsthat cannot support them for either passage or landscapeconnecting purposes. At least in terms of gnatcatchers,

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these corridors may function as ways for a species to getfrom one core site to another. Banded birds have beenrecorded as traveling from opposite ends of such linkages.Most links, however, do not provide true connection.Those with major four-lane streets and crosswalks as junc-tions would exclude animals other than birds. Thus, inthese cases entropy rather biology determines successfultraverse.

New Roles for Habitat Conservation Plans

HCPs should be complementary to species RecoveryPlans under the Endangered Species Act, rather than asubstitute. As such they should provide backup refugiawithin a larger context of recovery-based habitat pre-serves. HCPs should have buffers around them to protectthem from intrusive external damage, such as to water-shed problems of pollution and sedimentation, adjacenturban development, or other anthropogenic activitiesthat degrade the HCP over time. It is certain that surpriseswill happen, ranging from new exotic plants and animalsto the decline and endangerment of many species withinlimited, fragmented habitat, such as sage scrub, to otherless predictable occurrences, such as the effects of globalwarming and climate change. Within this context, speciesthat are sensitive now must have adequate areas of criticalhabitat and backup refugia. Ideally, HCP sites would bedistributed throughout the range or be focused on areaspoorly represented by designated critical habitat, as the“large preserve concept” (NCCP) cannot capture the ge-netic diversity or protect adequate numbers of broadlydistributed but rare taxa. HCP settings are an opportunityto be genetic repositories for site-specific salvaged plantmaterial, which would serve to both provide added habitatto a site and retain and preserve genetic resources thatotherwise would be lost. HCPs should have managementgoals, including the ability to manage a site differently ifneeded as more is learned about habitat and specieswithin them; i.e., adaptive management.

Conclusion

In conclusion, restoration of CSS in southern Cali-fornia lacks adequate consideration of the landscapescale and fire cycle characteristics. Canopy projects withestablished dominant shrubs are now expected by reg-ulatory agencies overseeing mitigation requirements,but the chances for integrating the diverse understoryflora are uncertain, particularly in its postfire cycles.Because the federally listed vertebrate fauna primarilyuses the perennial canopy shrubs, it is not likely thatmitigation for them will expend the long-term fundingneeded to assure full community presence in these

created habitats. Until whole community values areappreciated and required, it is probable that most ofthe “restoration” now occurring will yield exotic-filledunderstories with native plant canopies for the foresee-able future. It is not known how functional such skeletalcommunities will be, but it can be hoped that at leastbirds and large predators will be able to use them as atthe least as dispersal routes. Canopy projects are, how-ever, well suited to softening edge effects in habitatfragments, provide areas into which adjacent CSS caninvade—thus extending habitat—and can serve as ge-netic preservation of plant material that otherwise islost. HCP sites can play a strong role in these efforts.

Challenges, among the many, include (also seeNCCP Core Group 1997):

● Historic habitat loss, weeds, nitrogen deposition,foliar damage due to air pollution, habitat fragmen-tation, edge effects, and so forth

● Compensatory mitigation is often confused with res-toration, but their scope is very different and allowsvery incomplete efforts, monitoring, and long-termcommitment toward broad ecological goals basedon whole community presence and function

● Mitigation (replacement) is driven by such laws asthe Endangered Species Act

● Usually “restorations” are targeted toward canopyprojects and enhancement of target vertebrates, notwhole community concerns

● New approaches should include direct emulation ofmosaics of vascular plant species associations withinnearest neighbor stands

● Salvage of canopy and understory material providespatches of shrub habitat in large projects

● Restorations of CSS must include burning, thensome approach toward introducing fire-followingand subsequently appearing taxa

● Site-specific seed sources must be used (nearestneighbor approaches)

● Restorations must use models of emulations basedon near neighbor sites in natural condition

● Fidelity to exposure, aspect, and soil type

Acknowledgments

I gratefully thank the University of California Natu-ral Reserve System’s San Joaquin Marsh Reserve forcomplete computer support for this paper. A grantfrom the Transportation Corridor Agencies also madethis work possible. I am grateful to Joy Zedler and ananonymous reviewer who made extremely helpful com-ments on the paper.

S94 P. A. Bowler

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