Borrego Desert: Geographic Distribution Maps of GPS Points for Plant Species

In November, 2015, we have begun putting distribution maps online for some species, whenever they pique our interest enough that we wanted to see a map for ourselves. We had intended to wait until we had completely digitized our GPS records, but even our half-digitized database is complete enough to show the basic distribution of most species in the Borrego Desert.

The purpose of this page is to explain some of the properties of those distribution maps, the species GPS points, and to provide maps of all GPS points for all species to be used as a comparison to the distribution maps for individual species.

Our distribution maps have a number of advantages over the species distribution maps made from vouchers:

Just to be clear, voucher distribution maps for species are wonderful things, especially on larger scales than considered here, and we use them all the time as an invaluable tool. For more information, see Some Things You May Not Have Known About Vouchers.

As of 29 November 2015, we have digitized 9,473 GPS points from our surveys. The records range from -9 feet elevation near the Salton Sea to 5,349 feet at Whale Peak.

There are a number of things to be kept in mind about these points:

In the geographic distribution maps for each species, we also give the number of GPS points for each species, and the elevation ranges in our records for the Borrego Desert area. Since we have surveyed a number of areas just outside our definition of the Borrego Desert area, we include elevations of points from those areas.

If the records show a fairly-continuous distribution in elevation, a single range is given. If the lowest elevation records, and/or the highest elevation records, do not show a fairly-continuous distribution, those outlying records are given in parentheses, so that one knows the elevations at which a given species is commonly seen.

Fig. 1 shows maps of where we have digitized records as of 29 November 2015. Due to limitations of the points to Berkeley Mapper software used to produce these maps, only a representative one fourth of all our GPS points are in the linked maps.

Fig. 2 shows more detailed maps of where we have digitized records as of 7 January 2016, this time with all points used in the map.

These maps are useful in understanding the maps of individual species, since one can use them to see at a glance where we have surveyed and have not found a given species. When our database is complete, they will also be useful for seeing what areas have never been surveyed. Some of those areas can be targeted for future surveys, but some areas are so inaccessible that they might only be surveyed by drones.

Conventional maps showing species distributions only show where a species has been found. Other areas in such maps may simply not have been surveyed, so that one doesn't know if a species occurs in those areas. The maps in Fig. 1 explicitly show where we have surveyed for all species. Any areas shown on those maps, that do not have corresponding points shown on the map for an individual species, are areas where that species is likely not to exist, at least if it is a species whose occurrence can be noted during the time of the survey. Annuals that leave no trace in their dead form are the major exceptions here, since some areas have not had surveys done at prime time in a good rainfall year.

See also Preliminary Analysis of Elevations of the Species in the Flora, done on 5 February 2014 when the database contained 6,106 points, about 2/3 of the number of points now in our database.

Fig. 1. Geographic distribution maps for areas where we have digitized our GPS points from our surveys as of 29 November 2015. Due to limitations of the "points to Berkeley Mapper" software used to produce these maps, only a representative one fourth of all our digitized GPS points are shown.

Fig. 2. Geographic distribution map for areas where we have digitized our GPS points from our surveys as of 7 January 2016.

More detailed scale maps of the GPS points as of 7 January 2016 are linked below; these maps also show routes we have surveyed but for which we have not yet digitized our GPS points. There are 11,521 digitized GPS points in this data set, from 104 full surveys.

Some surveyed routes not yet digitized in each of those areas are:

Areas to survey in future

The following are some areas where we will try to get GPS points in the future, to make the coverage of the Borrego Desert more complete (only the Borrego Desert areas below 3000 feet elevation are listed below):


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Copyright © 2015-2016 by Tom Chester, Mike Crouse, Kate Harper, Adrienne Ballwey, and James Dillane.
Commercial rights reserved. Permission is granted to reproduce any or all of this page for individual or non-profit institutional internal use as long as credit is given to us at this source:
http://tchester.org/bd/species/geographic_distribution_maps.html
Comments and feedback: Tom Chester
Updated 12 January 2016