The Challenge of Vegetation Management at
the Local Level1
Thomas Oberbauer and Michael Evans2
Planning for vegetation management at the
local level can be as complex a process as at
the State or Federal level. Most Mediterranean
vegetation occurs as a mosaic of vegetation
communities arranged in an intricate manner
over a variety of topographic features, soil
types and climatic patterns. In many
Mediterranean climate areas, developments for
agriculture, suburbanization and industrial
uses have substantially intruded into areas
with native shrub ecosystems. This has
resulted in substantial losses of certain
vegetation and wildlife habitat types and has
increased wildfire control problems considerably.
A variety of tools and techniques can be
utilized to help insure that some resources
in Mediterranean ecosystems can be preserved
in a naturally viable state. In the following,
we examine examples of sensitive Mediterranean
ecosystems from the San Diego County region,
and describe some of the tools and techniques
that may be used in protecting these ecosystems
at the local and regional governmental level.
VEGETATION TYPES
Climate conditions in San Diego County,
California, range from relatively dry coastal
areas with warm dry summers and cool winters
to moist mountain areas with cold winters and
warm summers. During the late summer and
early fall, hot dry wind conditions occasionally
occur; these conditions are a major factor
influencing the occurrence of fire. Soil
factors, precipitation, temperature patterns
and climatic evolution have resulted in a
diversity of vegetation communities classified
1
Presented at the Symposium on Dynamics
and Management of Mediterranean-Type
Ecosystems, June 22-26, 1981, San Diego,
California.
Abstract: Several Mediterranean ecosystem vegetation types in Southern California have been significantly reduced in extent and viability in recent
years. These reductions have occurred because of
conversion to agriculture, residential uses and
support facilities, and habitat management by public agencies. Measures to control loss of sensitive
vegetation on privately owned land are limited.
Resource Conservation Areas (RCAs) identified in
the County General Plan are one planning tool to
distinguish areas of outstanding resource value.
San Diego County has applied several techniques to
conserve such scarce resources, including large or
clustered lot zoning or open-space easements.
as Mediterranean-like. However, a number of
these vegetation community types have been
significantly reduced in extent and quality
within recent historic times. Thus, some of
these communities have become increasingly
sensitive to human-caused disturbance.
Examples of sensitive Mediterranean
vegetation communities in San Diego County
include Coastal mixed chaparral or maritime
chaparral (Axelrod 1978), the Diegan subunit
of Coastal sage scrub (Griffin 1978), Southern
oak woodland, Riparian woodland/gallery forest,
Vernal pools (Barbour and Major 1977),
vegetation adapted to unique soils (eg., derived
from gabbro and metavolcanic rocks), and other
Mediterranean ecotypes that serve as habitats
for wildlife sensitive to disturbance or of
limited distribution.
Coastal mixed chaparral or maritime chaparral
is a woody shrub community found in cool coastal
areas which contains a large number of endemic
species of plants. Coastal mixed chaparral
may never have been widespread but it has
been further reduced by development so that
today it exists on about 2000 acres along
3
the coast of San Diego County. Coastal sage
scrub is a drought-deciduous shrub community
that has been heavily impacted by development
with as much as seventy percent of its
3
former areal extent obliterated. It
previously occurred in summer-warm valleys
near the coast and interior. Vernal pools
are a specialized Mediterranean vegetation
type in which plants are adapted to winter
inundation and summer desiccation. Shrub
vegetation, gabbro and metavolcanic soils
are often habitats of very limited distribution
found in the foothills of San Diego County.
Gabbro and metavolcanic habitats, as well as
vernal pools, contain a large number of
restricted endemic species of plants.
Sensitive Mediterranean habitats which
support specialized wildlife include Riparian
2
Environmental Management Specialists,
County of San Diego, 5201 Ruffin Road, San
Diego, California 92123
Gen. Tech. Rep. PSW-58. Berkeley, CA: Pacific Southwest Forest and Range
Experiment Station, Forest Service, U.S. Department of Agriculture; 1982.
3
Oberbauer,
in prep.
523
and Oak woodlands as well as some microhabitats of more widespread community types.
For example, the Gray vireo (Vireo vicinor)
appears to be limited to mature stands of
montane chaparral in the southwest United
States.
FACTORS INFLUENCING VEGETATION
The vegetation communities in San Diego
County considered sensitive are spread
throughout all portions of the region. This
distribution pattern undoubtedly occurs in
other Mediterranean climate areas throughout the world. Unfortunately, in areas
with pressures for development, this pattern
makes it extremely difficult to protect
these resources with large viable habitat
areas.
The recent loss of vegetation communities
in the San Diego region has resulted from
destructive human uses, including overgrazing, sand mining and flood control,
improper fuel management and inundation
from dam building. However, agriculture
and residential development have been the
primary causes of the destruction of
vegetation communities in the San Diego
region. Clearing for avocado planting has
destroyed nearly 35,000 acres of chaparral
in northwest and central San Diego County
4
in recent years . At the present time,
agricultural production on marginal soil
and steep slopes continues to cause the loss
of substantial amounts of chaparral and sage
scrub each year. These areas would otherwise probably be unbuildable for residential
uses because of the steep slopes. Potential
future crops, such as Jojoba (Simmondsia
chinensis) or eucalyptus for firewood, have
the potential to substantially destroy even
more Mediterranean vegetation.
Land subdivisions for residential and
commercial/industrial development is a
major cause of the loss of Mediterranean
ecosystems, particularly near the coast and
in the coastal foothills of Southern
California. In these areas, habitat loss
has been 94% of the vernal pool habitat,
70% of Coastal sage scrub, and 60% of
3
Coastal mixed chaparral .
Economics and traditional building practices
have entailed carving the land to fit the
use, necessitating mass grading, sometimes
with cut or fill banks over 100 ft in height.
This results in direct loss of vegetation
3
4
Oberbauer, in prep.
San Diego County Department of
Agriculture, pers. comm.
524
for grading and indirect associated impacts
including siltation, erosion, off-road
vehicle impacts, increased wildfire frequency,
introduction of cats and dogs, indiscriminate
trash dumping, etc.
Besides "urbanization", with dense types
of development, another significant factor
in the loss of Mediterranean ecosystems in
the San Diego region is rural residential
development (at a density of less than one
dwelling unit per acre). "Rural development"
results in widely scattered residential uses
interspersed in chaparral or sage-scrub or
live oak woodland communities. This pattern
of development also disperses the increased
potential of wildfire starts into the
surrounding shrub vegetation. The widely
spaced nature of these residential uses
makes them substantially more difficult to
protect by fire-fighting agencies when fires
do erupt. This pattern of development has
resulted in the need to reduce the wildfire
potential over very large areas of scrub
communities, to reduce fire damage to a few
scattered, although monetarily valuable,
residential improvements.
Large-scale vegetation management plans
have been proposed for numerous locations in
the Mediterranean shrub communities of
Southern California, in an effort to reduce
the potential life and property losses
associated in rural areas with large wildfires. These plans usually include, as a
major factor, a reduction of the volume of
flammable vegetative material (plants or
fuel) and to compartmentalize the vegetation
into generally controllable cells of
modified vegetation. Techniques of modification range from hand and mechanical cutting,
heavy grazing by goats, and more recently,
controlled burning. These types of vegetation
modification usually result in altered habitats
favoring wildlife species adapted to transitional habitats. These techniques are also
used for locally increasing populations of
game species. However, enhancing habitats
for one species usually means some detrimental
effect on other species adapted to the original
habitat. Inasmuch as the original habitat may
be depleted already, these detrimental
effects may he quite serious.
The frequency with which natural fires
occurred in the past has not definitely been
established for the majority of vegetation
types and geographic regions. Furthermore,
the effect of fuel or habitat management
techniques on sensitive plant and animal
species is poorly known. Because of underfunding and the short time available for
management implementation, there is little or
no chance to accurately assess either the exact
resources present before management controls
are applied, or the effects on sensitive species
after the vegetation management. It is likely
that there will be a continued loss of habitats
until more is known of species requirements.
From the preceding discussion, it should
be evident that some Mediterranean ecosystems
have been seriously damaged by human
influences, especially agricultural and
"urban" development. In San Diego County,
there have been attempts to apply various
methods to help control these losses. In
the remainder of this paper, we will discuss
tools available to local planners to control
the losses of sensitive Mediterranean ecosystems.
Using San Diego County as an example, we will
examine the application of these tools
through the planning process and some of the
problems and solutions we have encountered.
SOURCES OF INFORMATION AND PLANNING TOOLS
Data sources available for local planning
include the basic tools generally needed
for resource planning: Aerial photographs,
topography and soil maps, as well as reports
from governmental, academic, and conservation
institutions which deal with regional
resource identification. Frequently,
unpublished information may be available,
but it is often difficult to access,
interpret and evaluate. In addition, local
planning staff may not have the resource
data background to understand some
technical reports. In general the ideal
resource planner should have experience in
resource evaluation as well as traditional
planning concepts.
Local planners have a number of planning
tools to control and manage land uses. The
key tool for land use control in California,
as well as several other states, is the
requirement for local jurisdictions to adopt
a General Plan which guides land use
decisions. Such plans, containing several
elements (land use, conservation, open space,
transportation, etc.) establish long range
goals, objectives and policies. These goals
and policies guide land use decisions such
as zoning and discretionary projects and
set density limits, lot size and permitted
uses. The adopted land use map, which
identifies and controls land uses, is the
main focus of the General Plan. Content and
effectiveness of the General Plan depend on
the expertise of staff, degree and kind of
citizen involvement, and political complexion
of the decision-makers.
The Environmental Impact Report can also
be a useful planning tool. The EIR process
prescribes a standardized format whereby the
potential environmental impact of any
anticipated action can be evaluated and
whereby other agencies and the public can
provide information and opinion regarding
these future decisions and impacts. EIRs
are particularly effective when used to
forecast potential environmental consequences
of various planning strategies in a large
scale planning effort. However, the value
of environmental impact reporting can be
felt at all levels of planning and implementation, from the macro-scale (program planning)
through the micro-scale (implementation)
levels.
One of the most important problems with
any EIR process is that of eliminating bias.
Frequently the agency planning to carry out
an action is the same agency preparing
environmental analysis on the project.
Although the implementing party may best be
able to understand the project and its
objectives, their enthusiasm for the project
may make it difficult to be completely
objective in predicting the potential
environmental effects if a policy direction
has already been determined. If potential
environmental consequences are evaluated
from the very beginning of the decision
process in a step-wise manner, problems of
bias can be minimized. Environmental impacts
can be further focused as the project itself
is defined, all the way to the implementation
stage. Thus, the environmental review process
becomes an integrated environmental planning
process.
Model Plans
San Diego County, California is perhaps
typical of many western American situations.
For land use planning purposes, the 4,200square mile county is divided into community
planning areas based on geographic and
historic relations ranging from a few
dozen to several hundred square miles.
Since the late 1960's these community
planning areas have been systematically
planned in an evolving process as described
below:
Phase I: Collecting all known data useful
for planning, including previously prepared
planning reports, environmental impact
reports, aerial photographs, other natural
and cultural resource reports and records,
climatic and hydrology data, traffic, and
air pollution reports.
After an initial data survey, formal
meetings with area residents may reveal other
data sources and direct plan formulation.
This procedure helps focus on resources
and potential problems, and existing policy
framework, as it applies to the planning
area.
Phase II: Resource identification leads to
production of a constraints map by evaluating
resources and rating them for land use
limitations. This typically is done by
mapping constraints on transparent overlays
on a map of the project area. This permits
visual integration of various constraining
factors.
525
Phase III: Preliminary and alternative land
uses and residential densities are chosen
based on community input and resource
constraints.
Phase IV: These alternative plans are
shared with citizen's advisory committees,
who recommend other changes, which are
incorporated into alternatives for the
environmental studies or reports. At this
time the draft Environmental Impact Report
for the plan is written and sent out for
public review. Data used for resource
evaluation is the basis for the EIR. During
the public review period, comments and
additional information received are
incorporated into the Environmental Impact
Report.
Phase V: This report, and other social
and economic factors, are weighed by
elected decision-makers in adopting a plan
or combination of plans at public hearings.
Phase VI: Upon adoption of the General Plan
land use map and policies, detailed
zoning controls consistent with the plan
are adopted in public hearings. The environmental
document prepared for the General Plan remains
a useful source for individual project
environmental analysis. All future land
decisions must follow the goals, policies
and land use map of the General Plan.
The environmental planner or resource
manager tries to develop land use plans
which impact least on the most sensitive
and most limited resources, and require
the least amount of site preparation and
resource destruction for ultimate development.
Little research has been done concerning
the effects of various designs and strategies
of suburban and rural development on native
Communities, but theoretical works such as
those of Diamond (1975) on island biogeography
and the design of natural reserves appear to
have useful ideas. Generally, special concern
should be given to resources regionally in
short supply. The patterns and intensity of
uses in relation to the resources to be conserved
may greatly control impacts and thus conservation
effectiveness. Managing limited or potentially
endangered species on the habitat level is
preferable to later managing them as a single
species or even individuals.
THE SAN DIEGO COUNTY EXPERIENCE
The County of San Diego has developed a
process to identify and apply land use controls
to conserve certain limited or sensitive
vegetation communities and wildlife habitats
on privately owned lands within its jurisdiction.
Such resources are identified as Resource
Conservation Areas (RCAs) on the General Plan,
the principal land use control available.
526
Resource Conservation Areas outline geographic
areas that contain outstanding examples of
rare and endangered species habitats as well
as generally exemplary wildlife habitats.
Such areas are mapped from aerial photographs
and maps of collection sites of rare species
are field verified. Criteria for identification
of RCAs involve the presence of viable populations of rare and endangered species, areas
of particularly significant wildlife habitats,
of viable examples of vegetation types of
extremely limited distribution, such as those
discussed earlier in this paper. RCAs are
adopted by the Board of Supervisors as
part of the Conservation Element, a mandatory
element of the General Plan controlling land
use. Adoption as RCAs simply identifies the
presence of these resources to decision-makers,
land owners, planning staff, and other citizens.
Control to actually protect or conserve
resources so identified requires subsequent
action by the decision-makers, including
additional changes to the land use element of
the General Plan, further implementation
through rezoning, or project approval or denial.
RCAs play an important role in the environmental
review process by providing early identification
of critical resources which may require special
mitigating design. This enables all parties
concerned, including property owners, project
designers, agency staff, citizens, and
decisionmakers to review prospective
land use changes in the light of the
sensitivity of the identified resources.
At the same time, the Resource Conservation
Area concept can also be used as a focal
point to educate the citizens and decisionmakers of the value of their sensitive
resources. This is extremely important
because the greatest successes for environmental
controls generally take place in areas where
special efforts have been made to educate
the local property owners and citizens.
Further controls may be applied to
areas within RCAs, including special land
use (General Plan) designations, special
zoning regulations, large lot sizes or
requirements for clustering houses outside
of sensitive areas. The County has devised
a special overlay zone regulation called the
Sensitive Resource Regulator, to protect
vegetation types or habitats sensitive to
human impacts. This zone restricts removal
or addition of vegetation over areas larger
that 1000 square feet for any purpose without
an administrative permit subject to
environmental review. The County of San Diego
has thus far applied the Sensitive Resource
Regulator Zone to a few areas with unique
vegetation types and habitats of rare and
endangered plants. Mitigation of impacts
of proposed land use projects in such areas
may take the form of Open Space Easements
dedicated to the County, these easements
prohibit the removal of vegetation or the
placement of structures. Such easements
merely restrict destructive uses but do not
allow entry of the property by the public.
The property owner still retains fee
ownership.
Purchase of fee title is another option
for protecting endangered biological resources.
Private conservation foundations such as The
Nature Conservancy have expressed interest in
purchasing land with vernal pools, Engelmann
oak woodland, Coastal mixed chaparral, or other
isolated rare vegetation types. However,
because of the large amount of endangered
resources and the high cost of land in
Southern California, the actual amount of land
which could be purchased would be very small.
Therefore, protection of sensitive resources
on privately owned land is especially valuable.
The use of Resource Conservation Area (in
the General Plan) designations is one way
land use controls can be used to limit the
loss of resources, while still allowing the
owner a reasonable use of the land. However,
the successful use of these tools depends on
the information available, how it is used,
and on successfully educating the citizenry
and decision-makers about the importance of
these resources. Managing such resources
on private land must carefully weigh private
property rights and the public benefits of
conservation.
Therefore, there is a greater burden on the
manager of public lands to conserve these
limited resources. On public lands,
impacting uses are much more easily controlled
and there is an opportunity to carefully
evaluate the impact of various management
techniques. Detailed ecosystem-wide analysis
of the impacts of controlled burns and other
management techniques prior to their widespread
application can be carried out. Since public
land managers are acting as stewards for the
people of the State and nation, they have a
responsibility not to cause gross and irreversible impacts to any major part of the ecosystem,
particularly those resources limited in areal
extent and of high sensitivity. Given the
recent trends in destruction of Mediterranean
ecosystems in private ownership in California,
it is conceivable that public lands will be
the last remaining stronghold for these
ecosystems in any semblance of a natural
condition.
In summary, certain areas of Mediterranean
ecosystems such as southern California have
suffered extensive loss of sensitive resources.
The continued loss of these resources can be
controlled to a degree through the use of
planning tools. However, these controls can
only be effective if the political climate
favors resource protection. Education of the
public is the only way to effect the political
climate toward the concept of resource
protection.
LITERATURE CITED
Axelrod, D.I. The origin of coastal sage scrub
vegetation in alta and baja California.
Amer. J. Bot. 65(10):1117-1131; 1978
Barbour, M.J. and J. Major. eds. Terrestrial
vegetation of California. New York: John
Wiley and Sons; 1977.
Diamond, J.M. The island dilemma: lessons of
modern biogeographic studies for the design
of natural reserves. Biol. Cons. 7:129-146.
1975.
Griffin, J.R. Maritime chaparral and endemic
shrubs of the Monterey Bay Region, California
Madrono 25(2):65-81:1978.
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