Part of my reason for posting these monthly essays on NM plant communities was to get my own mind wrapped around the problem of where should we be putting our efforts, both time and money, into conservation. It's one thing to look at the individual rare plants listed at https://nmrareplants.unm.edu/ and another thing all together to look at them in terms of their ecological contributions. In turn, where can I as an individual make an impact?
Biodiversity is a critical part of sustainable development. A vibrant, diverse, and healthy environment provides everything from harvestable resources, nature tourism, wild genes to improve domestic crops, pest management, sources of medicine, and biologically-based environmental clean-up (https://doi.org/10.1098/rstb.1994.0089). Sustainable development and the maintenance or enhancement of biodiversity relates in little-explored ways to ecosystem function, stability and resilience.
The draft UN convention on biological diversity (CBD) sets out biodiversity targets for the end of the decade that include protecting 30% of land and sea, eliminating billions of dollars of environmentally harmful government subsidies, and restoring at least a fifth of degraded freshwater, marine and terrestrial ecosystems. The final version will be negotiated in Kunming, China, at the Cop15 summit, which is expected to be held at the end of August (2022). The CBD balances three main goals: conservation, sustainable use of biodiversity, and the fair sharing of benefits from genetic resources.
As I write this (3/28/22), BBC has published a primer on biodiversity at https://www.bbc.com/news/explainers-60823267. Without getting too deep in the weeds, they illustrate the key issues in five graphics. They define biodiversity as the variety of all life on Earth. It turns out, it's not that simple.
So what is biological diversity, that is, biodiversity? These essays on ecological regions, life zones, and community evolution with a focus on New Mexico have been using the term without formal definition.
For most people, biodiversity is simply the number of species in an area, which in the older ecological literature was called “species richness.” In a seminal paper by Harper and Hawksworth in 1994 (https://royalsocietypublishing.org/toc/rstb1990/1994/345/1311), only six years after Elliot Norse gave the term a proper definition in the literature, some important questions were raised: What is ‘biodiversity’? Is biodiversity just the number of species in an area? If biodiversity is more than the number of species how can it be measured? Are all species of equal weight? Should biodiversity measures include infraspecific genetic variance? Do some species contribute more than others to the biodiversity of an area? Are there useful indicators of areas where biodiversity is high?
Let's run through some of these...
A little reflection will show us that the number of species in an area isn't of much use, even though at first blush one might think otherwise. Because we tend to emphasis organisms that are visually obvious to us, we think of a landscape that is biodiverse as one with lots of differences at the macroscopic level.
But imagine an island with exactly two organisms. Are the following pairs all equally biodiverse?
A 'Gala' apple tree and a 'Honey Crisp' apple tree (different cultivars)
An apple tree and a rose (different genera in the same family)
An apple tree and a grass (different phyla)
An apple tree and a mouse (different kingdoms)
Obviously, a measure of biodiversity should take into account how different the various organisms are. A metric that uses increasing phylogenetic divergence or number of taxa or genetic variability might seem attractive but there are problems that for now we'll dismiss with a wave of the hand.
It would be handy to include some measure of infraspecific biodiversity in a particular location or population. At the BioPark Zoo, there are species survival plans (SSP's) for animals that take into account genetic relationships among a species across all collections at all accredited zoos to avoid inbreeding. Only recently have I read discussions about taking care to maintain genetic diversity among living collections in botanic gardens and arboretums.
Particularly worrisome in a world being fed increasingly by monocultures is the loss of genetic diversity in crops. One of the IUCN specialists at the BioPark recently gave a fascinating webinar on diversity or the lack thereof among apples and crab apples. Similarly, the NY Botanical Garden had a webinar on crop wild relatives with much the same message: we need wild species as genetic backstops for future agricultural improvements.
From my own experience as a horticulture postdoc at NMSU, we had assembled a large collection of onion genera in order to find genes for disease-resistance. Another professor collected field races of chiles in order to capture the variability within the species. In either case, the economic importance of the crops made the argument for conserving diversity.
But economic importance isn't the only metric for determining which aspects of biodiversity are “worth” conserving. We need the natural environment outside of agricultural production for a host of reasons ranging from recreation to climate moderation.
Turning our attention back to NM, Natural Heritage New Mexico out of the Museum of Southwestern Biology and Dept. of Biology at UNM have come up with a methodology for estimating biodiversity in areas of the state. Their biodiversity score (scale of 1 to 10) is an average of the scores for three factors: size, quality, and landscape integrity. The landscape integrity score is down-weighted by 50% to account for uncertainty in the accuracy of that layer.
Like our NY Times maps, NHNM used NatureServe maps where possible to generate Element Occurrences that defined populations of species of interest. Using some slick GIS tricks, this allowed them to generate Element Occurrence polygons that grouped populations together into areas of interest where their scoring methods could be applied.
One result is a map of NM that ranks areas of biodiversity. (I've slightly modified their color-coding to minimize the optically biased effect produced by their strong yellow color for moderate biodiversity. Instead, I've made 'Moderate' the palest color instead of the brightest.) The polygons are Important Plant Areas (IPA) and ranked by their Biodiversity Rank and Diversity Score. There are 150 IPA's in NM.
Within an hour's drive of Albuquerque, we find these IPA's:
23* Espanola to La Cienega
34* White Mesa
35 Lower Jemez River Valley
36 Espinosa Ridge
42 Rio Puerco / Rio San Jose
43 KAFB
44* Sandia Mtns
45 South Mtn
55 Rio Grande at Belen
56 Sevilleta Basin
142 Socorro and Strawberry Peaks
*Indicates IPA with outstanding biodiversity rank.
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