Transcript Searching for Patterns in Evolutionary Trends of

Geographic data:
sources and considerations
Geographical Concepts:
• Geographic coordinate system:
defines locations on the earth using
an angular unit of measure, a prime
meridian, and a datum
- datum: defines the position of the origin
and the orientation of latitude and longitude
lines
• Map projection: mathematical
transformation of the threedimensional surface of the earth
into a flat map sheet
Types of spatial data in GIS
• Vector data: points, lines, polygons
(shapefiles)
• Raster data: used in ecological niche
modeling for representing
environmental conditions (grids)
Raster obtained through interpolation Raster obtained through remote sensing
Example of interpolated surface from point data using Inverse Distance
Weighting technique. Courtesy: Science Applications International
Corporation
Characteristics of geographic data
• Quality: →Interpolated vs. remotely sensed
→Scale at which interpolation was done
• Spatial resolution – has to match the scale of the
questions we try to address with ENM
• Temporal resolution: can represent daily, monthly,
annual, or multi-annual averages
• Type: categorical vs. continuous (some ecological
niche modeling algorithms don't work well with
categorical data)
1.Quality: interpolation
WorldClim dataset: locations of climate stations
with precipitation data - 47,554 stations
WorldClim 1.4
Mean annual precipitation (1960-1990)
IPPC climate dataset: precipitation
data from 19,800 stations
2. Spatial resolution
• size of the cells in the raster
IPPC mean annual precipitation 0.5° resolution
WorldClim mean annual precipitation 0.008° resolution
Florida panhandle
3. Temporal resolution
• time period averaged (days, months, decades, etc)
MODIS EVI 15-30 October
MODIS EVI 30 October-15November
NASA/GSFC/University of Arizona
Climate projections
Mean maximum temperature (1960-1990)
Past climate scenarios
(e.g. Pleistocene)
Future climate
scenarios
4. Type
• Categorical data – correspond to
discrete fields; the values are assigned
to the entire cell area and represent the
category number
Land cover 2000
• Continuous data – surfaces, used for
natural (physical phenomena); the values
are assigned to the points and represent
the actual measured value
Digital elevation model
Points to keep in mind when
selecting geographic data for ENM
• Temporal and spatial resolution of geographic data has to match
those of species occurrence data; also, select a spatial resolution
that matches the question asked (e.g. continental spread of an
invasive species, vs. predicted distribution of a local endemic
species)
• Categorical data doesn’t work well with some niche modeling
algorithms; it is also difficult to match its temporal resolution with
occurrence data
• Remotely sensed data is powerful (no interpolation), but can only
be used with recent, up to date, species occurrence datasets
• When downloading geographic data, pay attention to projection
and datum, and any metadata available; some transformations
may be necessary
Sources of data
•Climatic (Global) data:
WorldClim current (1960-1990) climate data http://www.worldclim.org/
IPCC current and future climate data
http://www.ipcc-data.org/obs/get_30yr_means.html
http://www.ipcc-data.org/ddc_climscen.html
Climatic Research Unit http://www.cru.uea.ac.uk/cru/data/hrg.htm
Paleoreconstructions
PMIP http://pmip.lsce.ipsl.fr/
NOAA: http://www.ncdc.noaa.gov/paleo/
Sources of data
•Marine data:
NOAA World Ocean Atlas http://www.nodc.noaa.gov/OC5/indprod.html
Climate Prediction Center
http://www.cpc.noaa.gov/products/predictions/30day/SSTs/sst_clim.html
•Topographic and bathymetric:
USGS Hydro 1k http://edc.usgs.gov/products/elevation/gtopo30/hydro/
NOAA ETOPO www.ngdc.noaa.gov/mgg/global/seltopo.html
Bathymetry http://ibis.grdl.noaa.gov/cgi-bin/bathy/bathD.pl
Sources of data
•Satellite-derived (free):
Global Vegetation Indices:
MODIS http://edcdaac.usgs.gov/dataproducts.asp
(EVI and NDVI) 2000 to present
AVHRR http://edcsns17.cr.usgs.gov/1KM/1kmhomepage.html
(NDVI): 1985 to present
Global Land Cover:
IES Global Landcover 2000 http://www-gvm.jrc.it/glc2000/
University of Maryland (1992) http://glcf.umiacs.umd.edu/data/
Other data
WWF Ecoregions http://www.worldwildlife.org/science/data.cfm
UNEP IUCN Protected Areas http://sea.unep-wcmc.org/wdbpa/