People who have studied and thought a great deal about natural communities have created a system of nomenclature that has a hierarchy identifying areas with generally similar characteristics. These include geology, physiography, vegetation, climate, soils, land use, wildlife, and hydrology. Various authorities from the early 20th Century to the present have come up with systems of nomenclature to classify the spatial diversity of life on Earth. Terminology like biomes, ecoregions, ecosystem types, ecozones, biogeographical realms, life zones, ecological units, plant formations, and plant hardiness zones have been defined, often as part of a hierarchy.
Here I'm going to look at plant life in New Mexico, even though that's a particularly artificial political entity defined in 1912. My rationale is that this is the geopolitical unit where we (resident members of Native Plants of New Mexico) can have direct access to the levers of government, both by petition and vote. Thus, this is a level where we can have a significant personal impact.
True, we can and should make efforts at the local level (city and county) as well as at national and international levels. In fact, <spoiler alert> I believe that conservation of biodiversity can't be successful unless we take concrete steps at the very most local of levels, our backyards and porches.
We mistakenly believe that we need to save nature so that future generations can enjoy it. What we really need to do is save nature so that we have future generations.
Somehow, we've gotten this idea that humans and nature cannot coexist. The UN designates Biosphere Reserves as places of ecological significance. That language suggests there are places on planet earth with no ecological significance. Every square inch of the Earth has ecological significance, including our yards, including our corporate landscapes, including our roadsides, and even much of our agriculture. We can't just build biological corridors that connect natural areas, so that plants and animals can move back and forth between relatively small, protected, viable habitats. We need to create more viable habitats.
Stewardship of the Earth and conservation of biodiversity is not just something relegated to specialist biologists. Every single person depends entirely on the quality of our ecosystems, so why wouldn't everybody bear the responsibility of taking care of those ecosystems? It doesn't mean that you have to save biodiversity for a living, but you can save it where you live. One person can totally revitalize the their little ecosystem in their yard and enhance their local ecosystem.
This will bring us around to the questions of what is a native plant and why should I plant them in my yard or grow them in a pot on my apartment balcony? Gingkos used to grow in NM 7 million years ago. Are they native? Mesquite arrived 400 years ago. Is it native? Perhaps we're better off asking what ecosystem services a plant provides. What links in the damaged fabric of life does a particular plant create or strengthen?
Now that I've shown where I'm going with this series of essays, let's take a shot with analysis at the state level and see where it gets us in terms of conservation of biodiversity, especially native plants. If we're going to have a discussion about NM plant communities, it seems like we should start with the view from 10,000 meters (or 39,000 feet, if you prefer). From that point of view, we see things with the broadest of possible brushes. Let's start with ecoregions.
Ecoregions
At the most coarse set of divisions, Level 1, we see that NM has five ecoregions: Northwestern Forested Mountains, North American Deserts, Temperate Sierras, Southern Semi-arid Highlands, and the Great Plains.
This hardly captures the diversity that NM has. Level 2, with its slightly finer grain, catches more of this detail in six ecoregions. Now at least the North American Deserts have been subdivided into Cold Deserts (10.1) and Warm Deserts (10.2). These correspond to the Great Basin Desert and the Chihuahuan Desert. If I had to hazard a guess, I'd say that the dividing line runs right about through Polvadera, north of Socorro. The majority of our central and western mountains are now labeled Upper Gila Mountains. 12.1 in the extreme southwest is identified as Western Sierra Madre Piedmont.
By the time we get to Level 3 ecoregions, things are pretty stable, at least for NM in terms of number of regions – 8 of them. We have 6.2.14, the Southern Rockies up north and 10.2.4, the Chihuahuan Desert down south. To the east, the Great Plains have been resolved into 9.4.3, Southwestern Tablelands, and 9.4.1, the High Plains. 13.1.1 is now labeled as the AZ/NM Mountains. The Four Corners region is now considered the Arizona/New Mexico Plateau with a tiny sliver of Colorado Plateaus (10.1.6) wedged in along the CO border. 12.1.1 in the extreme southwest of the state is still Western Sierra Madre Piedmont.
Just considering the Sandia-Manzano Mountains behind the Albuquerque metro area, there's a lot going on that this ecoregion thingie misses. Anyone who has hiked the La Luz Trail can vouch for that. Similarly, hiking from Three Rivers Campground up to the top of Sierra Blanca takes you through a bewildering variety of life zones. What's going on here that the ecoregional model is missing?
