Atlas of Western Lichens

The world’s climate, we are told, is changing.

What this means, among many other things, is that our Atlas of Western Lichens project is long overdue. Lichens are about as close as living things get to being place. When places change, so do the lichens that inhabit them. And rapidly, too. Lichens are by far the most sensitive indicators of environmental change.

There are other good reasons for this Atlas project. For one, western North America supports one of the world’s richest macrolichen floras. For another, atmospheric conditions in this region are still largely unchanged from “pre-industrial” times – for which we can thank the Pacific Ocean. Finally, western North America supports an extraordinary number lichen endemics – species that occur only here. Providing maps for such species is one good way to sensitize resource managers to the need to conserve habitat on their behalf.

Mapping such a large region as western North America is not easy. To help in this task, we found it convenient to divide our region up into what we call lichen distributional units, or LDUs. At the present time we recognize 158 LDUs. Each LDU is meant to respresent an area having “uniform” lichen flora. That is, if a lichen is found at one location within a given LDU, then we hypothesize that it will be found in the same microhabitat throughout that LDU.

This is an important point to emphasize. Lichens, as much as if not more than any other life form, are very sensitive to environment at every scale, not just the broad regional scale on which our LDUs are drawn. To this end, each of our LDUs has been subdivided along several dimensions, such as basic vegetation type (alpine, high forest, low forest, and grassland), and soil type (acidic, basic, and circumneutral). See, for example, the maps of elevational subzones and major calcareous deposits below.

Now about frequency. Frequency is important to our project inasmuch as it serves as a rough surrogate for relative “fitness” in a particular portion of a species’s range. For our purposes, a lichen is “frequent” within an LDU when a lichenologist is likely to encounter it within an hour searching on foot. Species that can’t reliably be located within two days of searching are considered “rare”. Species having a frequency status between frequent and rare are termed “infrequent”.

Like other major online projects of this kind, ours will be interactive. Once it’s up-and-running, users will be able to compare and contrast the ranges not only of individual lichen species, but of any assemblage of species they want to think about. Lichen distribution can also be compared against an array of edaphic and climatic variables, including bedrock geology, soils, seasonal temperature, seasonal precipitation, and duration of snow cover.

That’s the good news. The bad news is that for the time being we’re able to post only a few of our maps – just enough, we hope, to give an idea of the kinds of analyses our website will enable. The rest will appear on line once Volume 1 of Ways of Enlichenment has been published. When will that be? Some time, we hope, in late 2012. If you’d like to be informed when the book comes out, please email us.

Here are a few sample maps to give a taste of what’s to come. Keep in mind these are just snapshots–the final product will be interactive.

Map of Elevation

Map of Elevational Subzones

Map of Snow Cover Duration

Map of Major Calcareous Deposits

Map of Major LDUs

Here is an example range map (using Leptochidium albociliatum to illustrate the process). The left map shows the initial LDU data we start with, the right map shows the final product that will wind up in the book. This is still preliminary, of course, pending further data checking. Click on the maps for more description.

Sample of Raw Range Data

Sample Completed Range Map