WLF 448: Fish & Wildlife Population Ecology

Fall 2011

Lab 3: Delineating Populations - Part 2

I. Delineating Population Distributions (species or subspecies)

A. Historic locations

B. Projecting from mapped habitat

C. Sampling for presence/absence

D. Other types of data?

II. Models

          A.  Deductive

        B.  Inductive

        C. Combination of deductive and inductive (e.g., Gap Analysis Project)

III.  Gap Analysis Project (GAP)

Scott et al. 1993.

GAP Analysis website (www.gapanalysis.usgs.gov)

A. What is gap analysis?

• Gap analysis is a proactive approach to protecting biodiversity. It seeks to identify gaps between land areas that are rich in biodiversity and areas that are managed for conservation.

  The GAP approach is based on three main assumptions: 

  • The best time to save species is while they are still common (i.e., to keep common species common).
  • It is cheaper to maintain natural populations, than it is to intensely manage endangered populations.
  • While we cannot perfectly model biodiversity, we can use what we know about the distributions of vertebrate species and vegetation types to assess biodiversity at local, state, regional and national levels.

B. How did GAP get started?

The gap analysis process was conceived in the 1980s. The roots of the program originated with application to Hawaiian bird conservation by J. Michael Scott. Later, he and other researchers at the University of Idaho Cooperative Fish and Wildlife Research Unit, initiated Idaho GAP as the first pilot under the U.S. Fish and Wildlife Service.

Until this approach was developed, there was no broad-scale way to assess the level of protection given to areas rich in biodiversity. Dr. Scott first used the methodology to focus on endangered birds in Hawaii. He began by mapping the distribution of each species individually. Then, he combined the individual maps to create a map of species richness throughout the island.  Scott found that fewer than 10% of the ranges of endangered forest birds were protected.

C. The goal of GAP

The primary goals are:

• to keep common species common by identifying conservation gaps

• to provide information about conservation gaps and biodiversity to the public so that informed resource management decisions can be made

• to facilitate the application of this information to resource management activities

In the past there was little information on ordinary species; their habitat needs had not been systematically documented, and there was little information about their overall distributions on lands that were being managed for conservation. There was no standardized classification system for species assemblages; and no institutional capability to develop or use the kind of information needed to manage biological diversity as a resource. These are the issues that gap analysis addresses.

D.  The Gap analysis method

Gap analysis consists of three main spatial data layers, a landcover layer, a layer showing the predicted distributions of vertebrate species, and a stewardship layer.

        1.  Map landcover of the dominant plant species. 

The first step of gap analysis is to map vegetation to the alliance level. Alliances are natural assemblages of plant species. They are used because the patterns of natural terrestrial landcover are a reflection of the physical and chemical factors that shape the environment of a given land area.  Plants also are determinate for overall biological diversity, as their structures and composition significantly affect species-level interactions.  

Landcover is mapped using satellite imagery (e.g., Landsat Thematic Mapper raw and hypercluster imagery from  the EROS Data Center). Other information sources include existing maps and other records, air photos, air video, and ground points.

        2.  Map predicted distributions of vertebrate species (i.e., amphibians, reptiles, birds, and             mammals).

All terrestrial vertebrate species that breed or use habitat in the state or region for an important part of their life history are mapped. All known, probable, and possible occurrences are used to define range limits. This step requires the active participation of vertebrate experts to determine the geographic range of each species, to help build the habitat relation models, and to review the draft maps. 

The information required to create these maps is extensive. In addition to the landcover maps created in the first step, information about the distributions of each species, lists of all native species, specimen collection records, range maps, and documented habitat affinities for each species must be collected.

Mapping predicted distributions starts with establishing the geographic range extent using the EPA's EMAP hexagonal grid or a more refined range map. The next step is to obtain all possible GIS coverages of features or conditions to which vertebrates can be associated. Then a Wildlife Habitat Relationship Model for each species is developed using the available coverage information, published literature and expert input. Finally, a database query is conducted to associate species with their geographic features, maps are output, reviewed, and refined. 

The products that result from this stage of the process include: 

• Habitat affinities models for each species

• Range maps showing the distributions of each native species

• Specimen collection records for each species

        3.  Delineate land stewardship at one of four levels. 

Stewardship is not the same as ownership. The land stewardship map combines attributes of ownership, management, and a measure of intent to maintain biodiversity. The term "stewardship" is used because legal ownership of a land area does not necessarily equate to the entity charged with managing the resource (e.g., land trusts and easements).

Gap analysis assigns a ranking of 1 to 4 for land parcels. Status 1 lands have the highest degree of management for conservation, status 4 lands have the lowest conservation score.  Levels 1 and 2 are the ones on which GAP bases its analysis of species protection. This allows identification of biodiversity gaps and can suggest strategies for filling them.

In assigning a stewardship ranking, the gap analysis process emphasizes the managing entity over the owner, and bases the ranking on the expressed long-term intent of the managing entity, instead of focusing on short-term processes. The criteria for assigning a ranking include: 

• Permanence of protection from conversion of natural land cover to unnatural land cover (e.g., human-induced barren, arrested succession, cultivated exotic-dominated).

• Amount of the tract protected, with 5% allowance for intensive human use.

• Inclusiveness of the protection (e.g., single feature--such as wetland--versus all biota and habitat).

• Type of management program and degree that it is mandated or institutionalized.

4.  To analyze the representation of vertebrate species and vegetation alliances in areas managed for long-term maintenance of biodiversity.

To accomplish this, maps showing animal and plant community distributions are intersected with stewardship maps to create tables of representation for each element. 

Types of analyses include: 

• Compare ownership/managing entities to biodiversity management status to answer the question:  "Where are the biodiversity conservation lands and who manages them?"

• Compare landcover types to stewardship to answer the question:  "What is the representation of each landcover type according to managing entity and management status?"

• Compare animal species distributions to stewardship to answer the question:  "What is the representation of each species according to managing entity and management status?"

IV.  Caution: Be a skeptic: