Posts Tagged: cattle grazing

Once perceived as a problem, conservation grazing by cattle a boon to vernal pools

Giving 1,200-pound cows access to one of California's most fragile and biologically rich ecosystems seems a strange way to protect its threatened and endangered species.

But a recently published study suggests that reintroducing low to moderate levels of cattle grazing around vernal pools – under certain conditions – leads to a greater number and greater variety of native plants.

“We found that after 40 years of rest from grazing, reintroducing conservation grazing had – across the board – positive impacts on vernal pool plant diversity,” said Julia Michaels, a visiting professor at Reed College who led a three-year study in a Sacramento-area reserve during her time as a UC Davis Ph.D. student.

Ecologists consider vernal pools – ephemeral ponds that form seasonally – “islands of native habitat” amid California's grasslands that are dominated by exotic grasses. These biodiversity hotspots harbor about 200 native species of animals and plants, such as the coyote thistle, which germinates under water and forms a snorkel-like straw to deliver oxygen to its roots – and then “fills in” its stem as the pool dries.

Specially adapted to survive in those stages of wet and dry, many of these species are found only in vernal pools scattered across California – making those pools an urgent priority for conservationists.

“It's estimated that more than 90% of the original vernal pools in California have been destroyed due to agriculture and urban development, so management of those remaining – including those that have been re-created – is of high concern,” said Valerie Eviner, a UC Davis plant sciences professor and UC Agriculture and Natural Resources affiliate. Eviner is a co-author of the study, along with UC Davis colleague Kenneth Tate, UC Cooperative Extension specialist.

During the 1970s and 1980s, vernal pools were fenced off in parts of the state, in the hopes of protecting the flora and fauna from grazing cattle. In the early 2000s, however, UC Davis researcher Jaymee Marty found that grazing was actually crucial to vernal pool biodiversity: once livestock were removed from areas that had been grazed historically, the diversity of plants plummeted.

“Her research was critical to rethinking the best ways to protect the diversity in California's vernal pool ecosystems,” Eviner said.

The Michaels-led study, published in the Journal of Applied Biology, builds on Marty's work, by looking at scenarios where cattle had been blocked from vernal pools for decades, and then observes the rate at which biodiversity returns after reintroduction of the animals. Michaels said she wanted to provide some initial answers to the practical questions that ranchers and land managers have in potentially reintroducing cattle.

“A lot of them had these areas that had been fenced off from grazing for the last 20–30 years, and they were very concerned about what happens if we let cattle back onto these vernal pool grasslands – are there going to be negative impacts because that land had been at rest for a few decades?” Michaels explained.

In their study within the Sacramento Valley, the researchers focused on transition zones – the “battlegrounds” between vernal pool native species and the encroaching invasive grasses, where they are able to detect most readily the effects of disturbances such as grazing.

They discovered that, after reintroducing cattle to areas that had been fenced off since the 1970s, there was a greater abundance of native flora (species like the vernal pool buttercup, bractless hedge-hyssop and bristled downingia), as well as increased diversity among the plants (both in number of species and in how evenly distributed they were).

“Encouragingly, diversity is rapidly restored,” Eviner said, “providing conservationists with strong data to show that rapid action can enhance plant diversity.”

And as for potential worries about cattle making a snack of vernal pool plants, Michaels and her colleagues observed that the cattle appear to be more interested in munching on grasses.

“Anecdotally, we saw very few signs of herbivory on the vernal pool species because the timing is such that [the plants] are underwater for a good part of the late winter and early spring, and then by the time they're blooming, there's plenty of good forage around for the cattle,” Michaels said.

In fact, the cattle seem to be performing a function filled for millennia by native grazers (namely, the once-abundant tule elk), helping to knock down vernal pool species' chief competitor in those transition zones: the grasses.

Although the researchers were concerned about a loss of biodiversity, excessive nutrients in the ponds due to defecation and harmful compaction of “fluffy” soil, none of their worries materialized on the test sites where grazing was reintroduced.

Instead, microdepressions created by the cattle appeared to encourage the proliferation of native plants. Each hoofprint became a miniature basin – “a vernal pool within a vernal pool.”

“Right in those transition zones, where they could be hosting either the vernal pool species or the upland grasses, just a couple centimeters of soil topography can make a big difference,” Michaels explained. “If a cow comes and steps in that transition zone, and that lowers the soil surface so it stays inundated a little longer, you end up seeing these pockets of vernal pool species that are able to persist.”

Michaels is currently conducting a follow-up study on the hoofprints to pinpoint their role in boosting native plant abundance and biodiversity. Because the prints can last for several years, they might be able to deliver some enduring benefits – and land managers might not have to bring cattle in to graze the pools as often.

“If it's really the hoofprints making the big difference, maybe we don't need to graze every year – only during certain times of year when we know the hoofprints will form well and harden, and then we're good for a few years,” Michaels said.

New UC ANR publication educates public on cycles of cattle production, grazing and economics

The pandemic has brought more people into nearby parks and public lands for hiking, biking and other recreational activities. In areas like the East Bay Regional Parks – a San Francisco Bay Area park system totaling more than 120,000 acres where about 65% of the land is grazed by livestock – visitors might see goats, sheep and, most likely, cattle.

Those encounters with animals (or their manure) represent a prime opportunity for members of the public to learn about agriculture and the ecological benefits of rangelands, according to Larry Forero, a UC Cooperative Extension livestock and natural resources advisor.

“In addition to supporting the raising of meat and other by-products, rangelands provide a variety of ecosystem services, including vegetation and watershed management, fire fuel control, and, increasingly, management of habitat for rare and endangered species,” Forero explained, noting that working rangelands cover around 40% of California's land area.  

As livestock grazing (mostly by beef cattle) constitutes a significant portion of land use across the state, Forero – along with fellow UCCE advisors Sheila Barry and Stephanie Larson – recently authored a UC Agriculture and Natural Resources publication summarizing the mechanics of cattle production.

“Beef Cattle on California Annual Grasslands: Production Cycle and Economics,” published in October and available as a free download on the UC ANR Catalog, describes the seasonal phases of cattle production and the factors that impact ranchers' financial calculations and management decisions.

“This concise publication walks through annual stock flows and calendar of operations and gives tables for estimating costs, return over cash, and gross income under various scenarios,” said Forero.

By covering care practices, infrastructure needs, grazing management and economics, Forero said the publication offers a succinct overview of beef cattle production and rangeland use for land managers, decision makers and the park interpreters (such as docents and guides) who educate visitors as well as the interested public.

“Even if only a relatively small percentage of park goers are interested, you still touch a lot of people with a document like this,” Forero explained.

He said he hopes park signage and QR codes will direct visitors to the publication for more information about the cattle and their seasonal movements.

“People often wonder where the cattle go when they leave the park and when they will return,” co-author Sheila Barry said. “The cattle may go to grass or feed yards in other places in California or even out of state.”

But, as this new UC ANR publication explains, the cattle production cycle turns over anew.

“There will be more cattle next fall, I promise,” Barry said.

Agriculture scientists positive about grazing

The Modesto Bee ran a story over the weekend with a headline that proclaims, "Experts positive about effect of grazing on land." It is remarkable, in my opinion, because scientists are so rarely "positive" about anything and are very adept at using conditional wording, such as seemingly, may be, could be, almost, nearly, etc. 

On the other hand, the headline writer may have been using the meaning of "positive" as merely the opposite of "negative."

The story was based on reporter John Holland's take on a recent Tuolumne County Resource Conservation District seminar, in which participants learned that  grazing enhances the foothill environment by controlling wildfire fuel and keeping imported grasses from overwhelming the native species. Cattle grazing also preserves open space.

"These are all privately owned landscapes that you are all managing for the greater good of everyone else," the reporter quoted UC Cooperative Extension farm advisor Scott Oneto.

According to the article, experts at the meeting said perennial native plants can thrive on grazed land because the cattle thin out the annual European grasses that have dominated the landscape since the 1800s. This improves habitat for squirrels and other small wildlife that sustain bobcats, golden eagles and other predators. Cattle, the story said, have taken on a role similar to that of buffalo on the Great Plains.

 

 

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