Dr. Debra Peters is a research scientist with the U.S. Department of Agriculture’s Jornada Experimental Range north of Las Cruces.
Peters said desert landscapes have changed in the past–and that can help us understand how climate change may impact vegetation.
Peters said a process called desertification turned the Jornada del Muerto more desert-like over the course of a century.
From the 1850s through the mid-1900s, she said factors like severe long-term drought and cattle overgrazing turned the region once covered by perennial grasslands into a landscape dominated by shrubs such as mesquite, creosote and tarbush.
“They were always here, they’re actually native species but they were in small abundances," Peters said. "So, they were scattered around and then they with many, many head of cattle and severe drought... the shrubs expanded and the grasses died out. And so now we have very few perennial grasses and lots and lots of shrubs and that’s the landscape that you see today.
But Peters said studies at Jornada have found changes in vegetation taking place since then, such as the introduction of novel species and the switch from shrub growth back to grasses.
“Our landscapes are very dynamic instead of just a one-way change from grasses to shrubs, they can go from shrubs towards grasslands, they can go between different shrub systems, they can actually have other types of grasses come in from South Africa. So, it’s a very dynamic system across the landscape. We talk about landscape change instead of just one direction which is desertification," Peters said.
She said the amount of precipitation southern New Mexico receives, about 9 to 10 inches a year, influences which vegetation grows.
For example, Peters said black grama grasslands flourished in 2008 after four wet years. Meanwhile, shrubs like mesquite increased following dry years. Those shrubs, Peters said, provide some benefits for the desert.
"The mesquite, actually the pods are really good for wild animals. The creosote and the mesquite actually hold the soil down right where they are. So, they’re not all bad right," Peters said. "And they’re not really going anywhere so we’re talking about our grasses sort of filling in the bare areas between the shrubs to reduce the soil and to reduce the erosion by wind and water, right. So, that’s the benefit that we get by putting more grasses back into the system.”
But record-breaking drought and increasing temperatures may make it a challenge for those grasses to grow.
According to the National Oceanic and Atmospheric Administration, Arizona, New Mexico and Texas had their second-hottest August on record in 2019. That followed a July that was the hottest month on record for the planet since record-keeping began 140 years earlier.
Regardless of how much rain falls in the desert, Peters said how landscapes respond is not only related to climate, but also the ability of plants to respond.
“How are the plants able to produce seed? How much they can actually grow? Are there even grasses there, right? Are the shrubs still living there? It just depends upon what’s happening on the landscape, not just is it going to increase or decrease in precipitation. So, it actually depends upon what the plants are doing and how much their ability to respond," Peters said.
How drastically the climate changes in the desert depends on humans’ ability to respond.
Dr. Peters’ presentation on landscape change will take place Sept. 12 at 7 p.m. in the auditorium at Doña Ana Community College’s East Mesa Campus.