* Critical Findings
Assessments
* Natural Diversity Database
* Terrestrial Vertebrates Restricted to the Sierra Nevada
MANAGEMENT STRATEGY
* SNEP Significant Areas Inventory
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MANAGEMENT STRATEGY
Biodiversity Management Areas
As summarized in the previous sections, human activities are exerting significant
impacts on native Sierran plant and animal biodiversity. In addition to outright
habitat conversion to residential or agricultural use, impacts accompany extractive
activities such as grazing and timber harvest. The effects of these activities, however, depend
on their timing, duration, and intensity. It appears that many native species are
compatible with renewable uses, given appropriate management practices. On the other
hand, SNEPs gap analysis indicates that many Sierran plant community types, which are
crude surrogates for total biodiversity, are not well represented in areas where
maintenance or restoration of native biodiversity is the primary management emphasis.
As a result, some environments and species are more vulnerable to conflicting land uses
than others, and there is very uneven knowledge of status and trends among community
types.
One strategy that could contribute to conservation of Sierran biodiversity would be
to improve the representation of plant community types in areas whose primary management
foci are restoration and maintenance of native biodiversity. Design and implementation of a system of such areas would likely require a large investment of land and
financial resources. Many questions would need to be addressed before committing
to such a system. Which environments and community types are most vulnerable and
in need of additional representation? How much area is required to meet specific conservation
goals? Where should new Biodiversity Management Areas (BMAs) be located? Can representation
of biodiversity be achieved using only public lands? How well could such areas address other concerns raised by SNEP related to forest structure, aquatic biodiversity,
and areas of special ecological interest?
Goals
The following pertain to all strategies using BMA methods:
1. Represent all plant community types, as defined by the state of California Natural
Heritage Division, in a regionally designed set of BMAs whose main objective would
be restoring and/or maintaining native biodiversity.
2. Locate the BMAs as efficiently as possible in terms of both size and suitability
of the area selected to meet a specified target for representation.
Possible Solutions
BMAs can be defined as specially designated public or private lands with an active
ecosystem management plan in operation whose purpose is to contribute to regional
maintenance of native genetic, species population, and community levels of biodiversity
and the processes that maintain biodiversity. Each BMA is part of a regional system of
BMAs and is located and managed to minimize the total risk to regional biodiversity.
A BMA may target specific organisms or community types for restoration and management
but not to the exclusion of other components of local biodiversity. Management may
include programs to test and refine best management practices for extracting renewable
natural resources. Economic activities are not necessarily precluded, but they are
subordinate to the goal of maintaining native biodiversity.
The system of BMAs is designed to be representative of biodiversity but is not intended
as a comprehensive reserve strategy that in itself can guarantee the viability of
the native biodiversity of the Sierra Nevada. The SNEP BMA strategy assumes that
the region will remain largely rural in character and managed for renewable resources in
a way that sustains many if not most elements of native biodiversity. Given this
scenario, a BMA system could not only provide sanctuaries for some species least
compatible with human activities in the region but also provide a kind of insurance policy for
maintaining native species and ecosystems. It is then largely a societal decision
how much land to allocate to BMA status.
Designing a BMA system requires definition of a planning region, a starting set of
BMAs, a set of sites within the region from which to select new BMAs, target levels
for representing plant communities in BMAs, a means of comparing the suitability
of different sites for BMA status, and a means of comparing the desirability of alternative
BMA systems that all meet the stated goal for representing biodiversity.
SNEP developed and tested a computer siting model to explore opportunities for a comprehensive
BMA system for the Sierra, in the following manner:
The range was divided into northern, central, and southern regions.
Each region was divided into planning watersheds averaging 7,500 acres in size. These
watersheds form the set of sites for selecting new BMAs. (Only entire watersheds
were selected.)
A watershed suitability index was devised based on human population density, road
density, the proportion of the watershed in private lands, and the degree of intermingling
of public and private lands.
Several starting BMA systems were compared. For example, one alternative assumed no
existing BMAs. Another considered all parks, designated nature reserves, and ungrazed
designated wilderness areas as BMA lands.
We compared two target levels for representing plant community types in BMAs: 10%
versus 25% of the distribution of each plant community type as mapped in the GAP
database.
The best (optimal) BMA system was the set of sites that required the least total area
to meet the representation target and also had the highest total suitability. (In
practice there is a trade-off between reducing the area required and maximizing the
suitability of the solution.)
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