For fans of Westerns, the vast, arid expanses of rural California may bring to mind cowboys, cattle, and tumbleweeds. But in times of drought, removing grazing animals from public lands leased to ranchers by the Bureau of Land Management is seen as the best way to help native grasslands survive.

A new report by the U.S. Forest Service shows there’s more to drought than withered plants and dry streams. Not only can drought lead to the accelerated onslaught of invasive plant species—including tumbleweeds, which originated in Eurasia—but it can slow nutrient uptake for native plants, increase risk of wildfires, and lead to wind and water erosion. To make a bad situation worse, on public rangelands grazed by cattle, poor management can “exacerbate the effect of drought,” according to the report, leading to the perception that “meteorological drought” is increasing in frequency.

In other words, the four-year drought that has decimated California’s water reserves (as well as those in other parts of the West) might be a bit worse in areas where cattle have been grazing—and federal land managers may recommend removing as much as 75 percent of the livestock on a plot to help it recover. Combine grazing with the high temperatures that exacerbated the drought over summer months—hot air holds more water, “making dry conditions relatively drier” according to the Forest Service—and the land may need more than the few months of rain that has finally been showering the West Coast to recover. On Tuesday, California’s State Water Resources Board voted to make only “modest adjustments” in the mandatory statewide reduction order put in place nine months ago, lessening conservation targets by a few percentage points in parts of Southern and Central California.

While reversing climate change and learning how to conjure rain from the skies are long-term ventures, taking cattle off land affected by drought is relatively easy. Native bunch grasses, which keep soil in place and prevent invasive species from growing, are attractive to cattle, said Randi Spivak, public lands program director at the Center for Biological Diversity. Cheatgrass, a particularly flammable invasive species, is public enemy No. 1 for Western rangelands. Spivak places it at the center of what she calls a “negative feedback loop.” Drought makes it harder for plants to grow, creating difficult conditions for livestock and native wildlife to find forage and cover—the fewer of these plants there are, the more cheatgrass takes hold. The land becomes more susceptible to fire, and when wildfires are sparked, they burn off the native plants, creating even more habitat for cheatgrass. “Cows and livestock should be excluded where native vegetation is still strong and cheatgrass hasn’t taken over,” Spivak concluded.

The U.S. Forest Service identifies the need to reduce cattle numbers on public land during a severe drought—in some cases to 50 or 70 percent of total carrying capacity (defined as the number of animals the land will support before causing environmental degradation) for the area. Plants that have been overgrazed “are less able to recover after a drought,” according to the Forest Service. This gives ranchers economic and ecological incentives to manage grazing lands carefully. Many ranchers turn to supplemental forage to augment the sparse vegetation available for grazing during a drought, but the Forest Service cautions that introducing supplemental feed can “potentially exacerbate the problem by maintaining an unsustainable number of animals.”

Sheila Barry, livestock and natural resources adviser for the University of California Cooperative Extension, agrees that ranchers will ultimately have to reduce herd size in times of extreme drought. However, “there is a lot of complexity people don’t understand,” she said. The cattle grazing on these lands are often destined to be finished in a feedlot, and in the first year of a drought, ranchers have the option of weaning cattle early to reduce the demands on the land without reducing total herd size. In the second year of a drought, however, ranchers have to consider cutting into their herd. “As soon as they do that,” Barry said, “it can take up to eight years to build it back.”

This is the crux of the conflict between environmentalists and ranchers. Is it better to keep cattle on the land and accept a longer recovery period for native vegetation, or protect the ecosystem to the detriment of ranchers who rely on the land for grazing?

It seems that we may already have an answer. In 2015, the annual commercial cow slaughter was at its lowest level in 10 years, according to a USDA Economic Research Service report. The gradual reduction in herd sizes has resulted in a 10-year low for cattle slaughter in the United States. Beef production has been so low that in 2014 and 2015, more dairy cows became meat than beef cattle.

However, Barry said, with the exception of lands with perennial vegetation that can be destroyed by overuse during a drought, “annual grasses are very resilient and come back.” She added, “Hopefully we’re learning enough to identify where those areas are to avoid permanent damage.”

Yet there are many who believe public lands are no place for cattle even during the best times. “Livestock grazing is very damaging in the arid West,” Spivak said. She said it requires nearly 14 acres of land to feed a cow and calf for one year in the West versus just two acres in the East. “They need that many more acres to roam around and find the grasses they like to eat,” Spivak explained. “The very grasses that prevent invasive species from growing and that wildlife need for cover.”