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Introduction
Native Landscape View
This page provides an overview of the approach and methodology
used to build the Native Landscape View of the EcoAtlas Baylands
and its current status as a tool for use in ecosystem analysis.
Process
The Native Landscape View of the EcoAtlas is a composite
picture based upon hundreds of independent sources of data.
These include eighteenth- and nineteenth-century maps, sketches,
paintings, photographs, engineering reports, oral histories,
explorers' journals, missionary texts, hunting magazines,
interviews with living elders, and other sources. Documents
were selected from about 10,000 materials examined at archives
around the Bay Area and are catalogued in the project databases.
Sufficient information about the natural Bay Area landscape
is available from early European documents to discover the
distribution and abundance of many habitat types fairly
confidently. With a robust amount of data, historical sources
overlap and confirm (or contradict) each other, strengthening
their interpretation. The intersection of discrete sources
is then mapped and recorded in a database. This is the basic
procedure used to compile the Native Landscape View of the
EcoAtlas.
Statement of Uncertainty: BEWARE
However, while the Native Landscape View likely approximates
pre-European conditions at a regional scale, with substantial
local detail, it must be emphasized that substantial uncertainty
may be present at a local scale. The amount of uncertainty
ranges from, in location, 100 ft to 1 mile, in size, from
10% to 100%, and in actual presence, from "definite"
to "possible." As part of the process of integrating
data to form the composite picture, the relative certainty
of each feature (e.g. a creek, marsh, or pond) has been
recorded according to quantitative or qualitative standards
(see Table 1) for presence, size, and location.
These individually coded attributes will enable EcoAtlas
users to query the estimated amount of uncertainty associated
with different places in the map, based on SFEI's scholarship.
However, these attributes have not been linked to the EcoAtlas
at this time. As a result, a wide range of certainty levels
exists in the Native Landscape View. Features may be as
far as one mile from their true 1800 location, as much as
half their true size, and/or not strongly supported (but
suggested) by the evidence.
Table 1. Certainty Level Standards (not
attached to GIS at this time)
| Certainty Level |
Presence of Feature |
Size of Feature |
Location of Feature |
| High |
Presence well-supported:
" Definite"
|
Size well-controlled
(+/- 10%) |
Location well-controlled
(within 500 feet) |
| Medium |
Presence well-supported,
with some qualification(s):
" Probable"
|
Size not well-controlled but evidenced
(+/- 50%) |
Location not well-controlled
(within 2000 feet) |
| Low |
Presence not well-supported:
" Possible"
|
Size not well-controlled and not evidenced
(defined case by case) |
Location not well-controlled
(within 1 mile) |
Data Gaps and Qualifications
While a tremendous amount of information about the historical
landscape has been gathered by a team of student researchers,
academic and agency scientists, citizen volunteers, and
SFEI staff, we suspect that as much or more knowledge about
the past landscape will emerge from local communities in
the future. We are establishing protocols to allow the EcoAtlas
to grow through local efforts, resulting in updated versions
and new understanding.
Each feature in the Native Landscape View of the EcoAtlas
has corresponding information, or attributes, indicating
its sources and the certainty of its presence, size, and
location.However, that information is not available in version
1.0 of the EcoAtlas. This means that a wide range of certainty
is associated with, but not indicated for, individual features
of the EcoAtlas. A general description of the origin of
each coverage and the uncertaintycurrently associated with
each feature type is given in the following sections.
- Historical Sandy Beaches of the San Francisco Bay Area
- Historical Lagoons of the San Francisco Bay Area
- Historical Intertidal Flats of the San Francisco Bay
Area
- Historical Tidal Marshland of the San Francisco Bay
Area
- Historical Tidal Marsh Pannes of the San Francisco Bay
Area
- Historical Seeps and Wet Soils of the San Francisco
Bay Area
- Historical Vernal Pools Soils of the San Francisco Bay
Area.
- Historical Vernal Pools Adjacent to the Baylands of
the San Francisco Bay Area
- Historical Perennial Palustrine Features Adjacent to
the Baylands of the San Francisco Bay Area
- Historical Sausals Adjacent to the Baylands of the San
Francisco Bay Area.
- Historical Riparian Forest Adjacent to the Baylands
of the San Francisco Bay Area.
- Historical Fluvial Features of Alluvial Plains of the
San Francisco Bay Area
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