‘Silent invasion’ of non-native plant species threatens Combat Center, other installation ecosystems

21 Oct 2005 | Lance Cpl. Brian A. Tuthill

In recent years aboard the Combat Center, a silent invasion has been underway that threatens to undermine and prevent the Marines here from fulfilling their training mission.

Invasive, non-native species of plants are impeding and the surrounding areas, including other military installations in the Southwestern United States.

“Terrorists or natural disasters jump to mind when picturing threats to military readiness and homeland security,” said Heidi Hirsh, natural resource specialist, Headquarters Marine Corps. “Few people realize that we also face the threat of nonhuman invaders. Invasive species are silently becoming entrenched in our ecosystems and pose a real threat to military facilities and readiness across the country.”

With the possibility of impeding on training obligations, one of the Combat Center’s major missions, it has gained much attention in recent years.

“The fact that we do have these invasive species on our land here has to be addressed,” said Maj. Jon Aytes, head of the Combat Center’s Natural Resource Environmental Affairs Division. “We started controlling these invasive species back in 1998.  Tamarisk, or salt cedar, has been the primary focus of our main efforts here.”

Tamarisk is a tree-like plant which can have a 200-foot-deep root system, sucking up available water from the ground and dispersing much of that into the atmosphere. Its name comes from the salinity of its leaves, which fall to the ground over a broad area and can make surrounding soil sterile over time.

“A big problem here is that our water is fossil water, where it is a prehistoric source that does not have a recharge,” said Dr. Marie G. Cottrell, natural and cultural resources officer for NREA. “What we have is what we have, and tamarisk can suck up a lot of water in a day.”

“The more that the water is depleted, the more minerals and salts get concentrated as the levels lower, changing the taste and quality of the water,” said Cottrell. “You end up having to build water treatment plants that cost more money. So every one of those trees we cut down saves a little bit of water that we can use for something else.”

Other invasive plant species that are aboard the Combat Center are the Saharan mustard, which can grow very thick and pose a potential fire hazard, and Russian thistle, commonly known as tumbleweed.

Tumbleweed, a thorny, green bush, easily breaks loose when it dies; it then blows across open areas and distributes seeds, as well as getting easily caught and stuck in equipment. Removal of its parts can be tedious with its sharp thorns, said Cottrell.

“These two plants are also the target of our current and future efforts here, but because of the sheer scale we cannot control all [species that are intruding],” said Aytes. “This includes Mediterranean and other grasses, as well as various puncture vines that are not indigenous to the land here.”

Another factor of concern arising from the growth of Saharan mustard is that the desert tortoise, a threatened species aboard the Combat Center, consumes these plants. The tortoise is then less healthy when it has non-native vegetation to feed on, said Aytes.

“For them it’s like eating junk food, they really don’t get many nutrients out of it,” said Aytes.

Tens of thousands of dollars are currently being spent here to control the spread of these species. For tamarisk, that money is spent on maintaining them by cutting them down and using herbicides; herbicides are also going to be used on other non-indigenous plants such as the tumbleweed and Saharan mustard. For now, the measures seem to be effective, said Cottrell.

“Our main goal is to provide troops with realistic training so they are prepared for their missions,” says Hirsh. “Controlling invasive species helps us do this, and at the same time protects the valuable natural resources that make America worth defending.”
Headquarters Marine Corps