The American Southwest: A gold mine of biodiversity plagued by the Anthropocene

January 7, 2021
headshot of Nargol Ghazian, with the ComSciCon-GTA 2020 logo to the upper left
Nargol Ghazian, York University (ComSciCon-GTA 2020)

by Nargol Ghazian (ComSciCon-GTA 2020)

Before my first visit to the region, most of how I imagined the American Southwest derived from classic western movies I watched with my grandfather as a child or, most recently, HBO’s dystopian-series Westworld. But upon arriving in the region, I quickly realised it is much more than a wild-west-themed playground, despite what the TV show may have us believe. The American Southwest is a hidden gem of floral and faunal diversity beneath a calm surface. This realisation inspired me to embark on a fascinating journey of discovery. 

The Southwestern region of the United States, commonly referred to as the American Southwest or more fittingly as the Desert Southwest, is a region that stretches from California to New Mexico, and from Colorado, Utah, and Nevada to the Mexican border. The region encompasses the biggest arid and semi-arid areas of the United States with the Mojave, Sonoran, and Chihuahuan Desert making up the greatest portions. The region receives very little precipitation, and most of the precipitation occurs in the high-elevation areas in the winter. Despite the harshness of the landscape, thousands of plants and animals in the region help each other through non-trophic (not related to the food web), positive interactions to increase their survival. Foundation shrub species for example can facilitate other taxa through various mechanistic pathways. Foundation species are species that are locally abundant, and like keystone predators, create stable conditions required by other species in the ecosystem. Foundational plants can include shrubs, perennials, trees, and cushion plants (a mat-like plant usually growing on rocks in alpine and sub-alpine Arctic).

Unfortunately, similar to many other global systems, drylands in the Southwest are not exempt from today’s ever-growing anthropogenic disturbances. Climate change in deserts and semi-arid regions is a rapidly growing issue; paired with factors such as land-use changes, including agriculture and industrial oil exploration, as well as wildfires, climate change can further decrease biodiversity by reducing the available terrestrial habitat for plants and animals. If we extrapolate the current trends, it won’t be long before fine-scale changes and fluctuations in climate further exacerbate species loss.

The Experiment 

Knowing the importance of vegetation shade, my colleagues and I at York University, Toronto, Canada set up an experiment to test whether artificial canopies function similarly to the canopy of resident native shrubs when improving the understory (ground-level) light and temperature regimes. We wanted to investigate whether artificial shelters are able to reduce the amplitude of variation in both above parameters, and function similar to natural shrubs. Our study took place in the spring-summer period of 2019 in Panoche Hills Management Area, a grassland located in the western edge of the San Joaquin Valley in California. We constructed artificial shelters using simple, affordable material such as PVC pipes and UV-permeable shade-cloths at three blockage percentages (15, 50, and 90 percent). The purpose of the experiment was to examine the efficacy of artificial shelters as a short-term intervention that mimic the natural variability in climate at fine scales and offers a refuge whilst managers and stakeholders in the region restore native vegetation. 

Our study showed that shelters offered more stable temperatures and reduction in light compared to open areas and that they provided a similar thermal and light habitat to established native shrubs. Shelters can function like vegetation in some capacities by increasing the thermal heterogeneity within a given environment, at least in deserts, which in turn offers greater resources for habitat selection. However, the next obvious step in the study would be to examine how animals interact with these shelters and to utilize more environmentally-friendly materials when construction them - This is precisely the focus of our newly proposed project. 

My experience working in the American Southwest taught me that there is a lot more to the region than meets the eye and that deserts are not ecological wastelands. In fact, the area is a treasure full of flora and fauna experiencing thousands of biological and ecological processes at any given time; you simply have to pause and look around you to spot a few.

The image on the left shows a small, white triangular shelter on a brown, grassy field, while the right image shows the same but the shelter is black
Left-Triangular shelter with 90% shade cloth attached to PVC skeleton using zip ties. Right-Rectangular shelter with 15% shade cloth attached to two PVC skeletal frames.

landscape photo of rolling hills without trees, green-brown grass, and small shrubs scattered
Panoche Hills Conservation Area, California.

landscape photo of a rocky, mountainous plateau type area, with shrubby cacti and other desert plants
Sweeney Granites Mountains Desert Research Center, Mojave Desert, California

landscape photo of a mountainous desert basin, with dry shrubby plat in the foreground and rocky peaks rising in the background
Sweeney Granites Mountains Desert Research Center, Mojave Desert, California.

----------------------------------------------

 

Nargol Ghazian headshotNargol Ghazian is a PhD Candidate at York University, Toronto, Canada. She seeks to understand how anthropogenic changes are impacting the natural word and strives to come up with active restorative solutions. When she’s not doing science, you can find her biking, cooking, and photographing the great outdoors. 

Twitter: @NargolG