Controlling Giant River Cane to Economic Advantage

By

Jim Earhart, Ph.D.

Director of the Rio Grande International Study Center Cane Control Project

Unfortunately for the vegetation and wildlife of the riparian habitat along the Rio Grande this American heritage river was made part of the border between the United States and Mexico. The historic economic disparity between the two countries, coupled with the recent “war on terrorism,” has created a “war” on water quality and habitat for native plants and animals along the river.

The United States Department of Homeland Security is spending large quantities of tax dollars to stop the flow of illegal traffic across the border. This expenditure includes a proposal to eradicate giant river cane (Arundo donax, A. donax) by mechanical removal with heavy equipment and by aerial application of a broad spectrum herbicide by helicopter.

We agree that this invasive plant provides concealment for illegal activity, replaces indigenous plants that provide habitat for native species, and uses large quantities of water that could be used by farms and cities, but we believe the means suggested by the federal government will be highly detrimental to the ecology of the Rio Grande.

River cane has replaced willow and other riparian trees that serve as sources of food and nesting for important bird species. Small U. S. populations of Groove-billed Ani, Altamira Oriole, Elf Owl, Ferruginous Pygmy Owl, Brown Jay, Gray Hawk, Chachalaca, Ringed Kingfisher, Hook-billed Kite, and White-tipped Dove are confined to a relatively small area in South Texas, mostly along the river. Increasing acreage of A. donax will be detrimental to these species. Cane should be controlled, but aerial spraying, the method of choice by Homeland Security, will kill native vegetation that serves as habitat for native species.

Giant river cane was introduced into the Americas by the early Spanish settlers who used it to construct crude housing, weave baskets and mats, make musical instruments, and, very likely, to feed livestock. Because of its prolific growth in warm, moist environments that lack natural enemies, A. donax has been far more successful in America than in its native Mediterranean region. Dense stands of the cane extend for hundreds of miles along the Rio Grande.

The Rio Grande International Study Center, in conjunction with Laredo Community College (LCC), is investigating the potential use of this invasive species of giant grass as food for livestock. Most local ranchers along the U. S. river bank do not graze livestock on the cane for fear of theft or for fever tick infestation or because they believe animals will not eat the cane.

Our work was stimulated by reports that goats have been used with some success in controlling cane growth in California. Furthermore, we have seen horses, goats, cattle, and donkeys drinking from the river in Mexico across from the LCC Campus and concomitantly we have observed very little cane growing on the Mexican river bank. Rather than cane the Mexican bank is lined with large trees that shade the flowing water.

These observations prompted two of our members, Tom Miller, Director of the Lamar Bruni Vergara Environmental Science Center and Dr. Tom Vaughan, Texas A&M International University Biology Professor to compare U. S. and Mexican cane growth by canoeing a 90 mile stretch of the river between Laredo and Eagle Pass.

They estimated cane cover on the U. S. river bank to be between 95 and 98 percent compared to three to five percent cane cover on the Mexican side of the river. During their three nights on the river they could find no place to camp on the U. S. side because of the dense cane and were forced to camp either in Mexico or on islands in the river. They reported no mammals on the U. S. river bank, either domestic or wild.

From our trials during the past two years we know that ram sheep, Spanish goats, Boer goats, and donkeys feed enthusiastically on A. donax. Poncho, one of our two donkeys, is thriving after almost two years of browsing and grazing primarily on river cane.

In our goat herd we now have one Billy, four nannies and three kids. Most of these goats have been feeding on the cane for about five months and appear healthy. Two of the nannies kidded while feeding on the cane and have produced vigorous kids.

Feral dog problems have prevented us from having more long term data on sheep and goats. We have taken steps to prevent predator problems by building more secure fencing, setting dog traps, and increasing surveillance by our volunteers and by U. S. Border Patrol Agents who have been very accommodating in helping us with the experiment.

We are working to answer other questions. For example what is the live stock carrying capacity of an acre of cane during different seasons of the year? In recent winter months the cane growth rate was low and two donkeys and five goats decimated one acre of cane in a few weeks. The animals had to be fed supplemental hay until they could be transferred to a new stand of cane. Now, April 6, 2010 seven goats and two donkeys are having difficulty in keeping up with the cane growth on the same acre.

There are numerous other questions to be answered. At what stage of development is the cane more attractive and palatable to the animals? What, if any, supplemental nutrients will be required for long term feeding with cane? How will the cane be replaced with native species?

Our work suggests one way in which cane may be controlled to economic advantage rather than spending large sums of taxpayer money and employing environmentally damaging techniques to control this invasive species.

We wish to honor Susan Porter Smith, environmental visionary, science research editor, and artist who founded Save the Laja, Inc., and to thank the organization she established for its financial support of the Rio Grande International Study Center’s river cane project to safely and effectively improve habitat along the Rio Grande by less environmentally threatening means.

Also, special thanks to Laredo Community College Intern Nelly Hays who enthusiastically expended much hard work to help make this project a reality.

Furthermore, thanks to Penny Warren, RGISC Board Member and expert birder, for her input on the writing of this paper.