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GAP: The First Ten Years

Getting off the Ground
The term “gap analysis” was first used by Burley in 1988 and put
into practical application in Mike Scott’s now famous Hawaii project
that identified the “gap” between bird distributions and conserva-
tion areas. Species distribution maps and land stewardship maps
were originally produced as Mylar overlays from extensive field
work, and The Nature Conservancy used these maps to establish
several preserves (Scott et al. 1987a). They were the basis for cre-
ation of new National Wildlife Refuges in Hawaii. It was Jack
Estes, a geographer, who suggested a Geographic Information Sys-
tem (GIS) approach to put the huge data set into a form that was
easily usable by managers.

When Mike Scott moved to California in 1986 to head up the Cali-
fornia Condor recovery program, it became clear to him that to
avoid such costly protective measures, species had to be protected
while they were still common. At a meeting in Denver, Scott dis-
cussed these problems with Blair Csuti, then a regional zoologist
with the Natural Heritage Program. They drew up an outline for
gap analysis, to be expanded into the seminal BioScience article
(Scott et al. 1987b) that presented the concept of gap analysis.

Scott tried to sell the idea to Defenders of Wildlife and the Fish and
Wildlife Service. He was able to obtain $36,000 from Idaho Fish
and Game and the National Fish and Wildlife Foundation to start a
gap analysis of Idaho. A breakthrough occurred when a presenta-
tion to a Congressional Working Group sparked enough interest to
put $300,000 as a line item in the budget of the Idaho Cooperative
Fish and Wildlife Research Unit to conduct GAP in Idaho under
Scott’s leadership. Csuti was hired to conduct a gap analysis in
Oregon. California was the next state to start a GAP project, led by
Frank Davis. Davis spent a sabbatical at the Idaho Coop Unit in
1992 and co-wrote a detailed description of the Gap Analysis Pro-
gram (Scott et al. 1993). Ted LaRoe, then Chief of Cooperative
Research Units, worked tirelessly on behalf of GAP and helped to
substantially increase funding.

Thus, a national program was born and grew, through the incre-
mental grassroots effort of scientists who believed in a proactive
approach to conserving biodiversity in the U.S.

As GAP developed beyond the prototype stage, its status as a basic
research project changed, and information collection activities be-
gan in more and more states. When the Department of the Interior
science programs were consolidated into the newly established
National Biological Service (NBS) in November 1993, GAP was
placed in the Division of Inventory and Monitoring. Ultimately,
the GAP program, along with the rest of the NBS programs, settled
in the U.S. Geological Survey in 1997.

Rising Projects, Falling Budgets

Budgets rose rapidly, nearly doubling every year from 1990-1995
(Figure 1). 

In 1994, GAP underwent a formal peer review (Zube
1994) and an independent review funded by the forest products in-
dustry (Flather et al. 1994). Both of these critical reviews recog-
nized GAP as a valuable tool but noted it was substantially
underfunded. Increasing with the budget was the number of state
projects, from the Idaho pilot in 1990 to more than 40 in 1995. The
year 1996, however, saw a decline and then flattening of the GAP
budget, presenting a major challenge to maintaining the multiyear
projects initiated during the previous years (Figure 1). 

Average funding per state was reduced along with budgets for research, ap-
plications, and extension activities.

Figure 2. Example budget allocation from 1998.

Partners Make it Possible

The strong partner collaboration of GAP at the state project level is
well known and certainly has been crucial in many states in provid-
ing contributions of funding and in-kind assistance. National part-
ners have also played a critical role. Over the years, GAP has re-
ceived funding from both the Department of Defense (DoD) and
the Environmental Protection Agency (EPA; Figure 3). These con-
tributions not only helped launch many state projects and aquatic
pilots, but also aided GAP in the development of the Multi-Resolu-
tion Land Characteristics (MRLC) Consortium. The MRLC formed
to make joint purchases of Landsat Thematic Mapper (TM) satel-
lite imagery covering all of the conterminous 48 states. A joint
purchase in fiscal year (FY) 1994 saved the government millions of
dollars in direct costs as well as an estimated 30 million dollars in
combined program costs (Jennings et al. 1995). The MRLC estab-
lished a common set of digital land cover data across multiple lev-
els of spatial and thematic resolution and developed a strategy for
integrating the land cover data from member programs into a single
national land cover database. GAP also partnered with the Federal
Geographic Data Committee’s (FGDC) Vegetation Subcommittee
to develop federal standards for natural land cover types and was
instrumental in development of FGDC metadata guidelines.

Currently GAP is working to develop core partner funding for re-
gional mapping updates such as Southwest Regional GAP (SW-
ReGAP). For example, EPA staff will act as principal investigator
on the project and may contribute significantly to the total cost.

Figure 3. Funding for GAP projects received from EPA and DoD
between 1994 and 1999.

Successful Innovations

One goal of the state-based business model for GAP was to engage
numerous investigators at a variety of institutions to create novel
data sets on a scale never before attempted. To a large degree, this
has succeeded. GAP investigators pioneered the development of
airborne video for land cover mapping and accuracy assessment.
The application of airborne video for GAP land cover mapping was
begun by Graham (1993). Since then, Slaymaker (1996) has fur-
ther improved the application of airborne video to object interpre-
tation. A review of GAP land cover mapping protocols (Eve et al.
1998) found that the mapping effort has resulted in several positive
developments, such as laying the groundwork for further advances
in land cover mapping, stimulating cooperation and collaboration
in mapping, increasing the acceptance and adoption of remote sens-
ing and GIS as mapping tools, and assisting in the development of
numerous new techniques for land cover mapping. In this bulletin,
Homer and Crist trace the developments in land cover mapping
over the past 10 years in more detail.

Sound methods were also developed for modeling predicted ani-
mal distributions, and further work by Haithcoat (Drobney et al.
1999) and Edwards (1996) continues to push such modeling to-
ward greater thematic detail and precision. (See “Experience and
Trends in Animal Distribution Modeling in the Gap Analysis Pro-
gram” below). Stewardship mapping and gap analysis methods
were standardized and refined but to date have seen less research
and development, as discussed in the article “Identifying the Gaps,
Locating the Reserves: Some Thoughts on Getting Gap Analysis
into Conservation Practice” below. More recently, however, GAP
project leaders and their cooperators have increased their interest

and work in analyses and application to conservation (see Capen
and Stoms et al. below).

Guidelines for conducting aquatic Gap Analysis projects were de-
veloped by pilot projects in NewYork (Meixler and Bain 1998) and
Missouri (Sowa 1998). Though GAP has not yet been able to gar-
ner core funding for the aquatic component, it continues to develop
methods that will lead to national standards and protocols when a
national strategy emerges.

Putting GAP to Use

Despite the fact that GAP is only this year publishing the bulk of its
data, participants, cooperators, and others representing a wide spec-
trum of interests have made significant use of the information in
hundreds of applications at a variety of scales. These uses include
wildlife management, ecosystem restoration, county planning, land
use planning by private corporations, basic research, generation of
options for large-area designations, and environmental assessments.
A typical application of GAP data is developing a prototype con-
servation planning process for the Columbia Plateau ecoregion. The
goal of this effort is to find the most efficient method for designing
and assembling a portfolio of sites to maintain all viable native spe-
cies and community types within the target ecoregion. Such a
method would maximize the biodiversity protected relative to the
number of conservation sites or extent of land area. GAP data have
also been used for more unusual applications, such as developing
natural systems agricultural practices that provide habitat for birds
that prey on insect pests and integrating the needs of these bird
species with those of agricultural production. Another example of
an ancillary application is assessing possible methods to reduce deer/
vehicle accidents on Iowa highways. By evaluating land cover ef-
fects, areas that have a higher probability of deer/motorist encoun-
ters can be identified. These examples and many other GAP appli-
cations can be found on the GAP home page.

Where Are We Now?

GAP is now active or completed in all 48 conterminous states and
Hawaii, and interest is high to initiate Alaska and several U.S. terri-
tories as funding becomes available. Updates have been conducted
in Idaho and Oregon and initiated in five southwestern states. (For
current status and anticipated completion dates of GAP projects in
the U.S. see the map on page 58). By the end of calendar year
2000, it is anticipated that 35 states will have been completed and
published on CD-ROM and the World Wide Web. These include:
Arizona, Arkansas, California, Colorado, Connecticut, Delaware,
Florida, Idaho, Indiana, Iowa, Louisiana, Maine, Maryland, Mas-
sachusetts, Mississippi, Missouri, Montana, Nevada, New Hamp-
shire, New Jersey, New Mexico, New York, North Carolina, Okla-
homa, Oregon, Pennsylvania, Rhode Island, Tennessee, Texas, Utah,
Vermont, Virginia, Washington, West Virginia, and Wyoming.

We can also view GAP progress outside the state context and in a
national perspective. For example, 75% of land cover mapping of
the conterminous 48 states is complete (Figure 4).

Figure 4. Current status of GAP land cover mapping across the U.S.

No one agency can claim to be GAP—it is truly collaboration on a
national scale, its success the work of many. Individual GAP re-
searchers can be proud of both their contributions to the national
database and their intellectual contributions that have paved a once
rocky road for current and future researchers. Still, this reflection
on GAP’s past ten years would be incomplete without an
acknowledgement of the early leaders and researchers who made it
possible. Mike Scott, Blair Csuti, Frank Davis, and Jack Estes de-
veloped the early concepts and founded the pilot projects; Steve
Caicco, Tom Edwards, and Jimmy Kagan took on the daunting task
of mapping the first few states with no models to guide them; Mike
Jennings started and shepherded dozens of projects, guided the pro-
gram through several administrative changes, and obtained the co-
operation of the major national partners in the important MRLC
and National Vegetation Classification initiatives. Credit is also
deserved for the agency administrators, including Amos Eno, Doyle
Frederick, Ted LaRoe, and John Mosesso, who worked within the
bureaucracy to support GAP and keep it growing. Finally, we must
acknowledge some tireless friends who guided and lobbied for GAP
throughout the early years, including Sara Vickerman of Defenders
of Wildlife and several folks from The Nature Conservancy includ-
ing Denny Grossman, Craig Groves, Deborah Jensen, and Larry
Master. There are many other guiding lights, particularly at the
state level, that cannot all be listed here. However, recognition of
the hundreds of dedicated graduate students is certainly well de-
served.

Our discussion continues on the following pages with the thoughts
of Mike Jennings and others on “GAP: The next ten years” and
goes into more depth with articles on the history and future outlook
for land cover mapping, animal distribution modeling, and stew-
ardship and analysis.

Literature Cited

Burley, F.W. 1988. Monitoring biological diversity for setting
priorities in conservation. Pages 227-230 in E.O. Wilson, edi-
tor. Biodiversity. National Academy Press, Washington, D.C.