Economic Implications of Biological Control of Arundo donax in the Texas Rio Grande Basin
Abstract
ABSTRACT
Arundo donax, or giant reed, is a large, bamboo-like plant that is native to Spain and has invaded
several thousand acres of the Rio Grande riparian zone in Texas and Mexico. The plant grows to
over 26 feet tall, and consumes large quantities of water, estimated as an amount equivalent to
about 11% of irrigation water diverted by Valley irrigation districts (i.e., some estimates are more
than 5.5 acre-feet per acre). With concern of increased water demands in the Texas Lower Rio
Grande Valley region, the United States Department of Agriculture, Agricultural Research
Service (USDA)ARS) is investigating four herbivorous insects as potential biological control
agents for Arundo donax to facilitate increased water supply.
This study examines selected economic implications for agricultural water users in the United
States of applying these biological control agents along the Rio Grande. The research includes
(a) estimating the value of the water saved due to the reduction of Arundo donax, (b) a benefit
-cost analyses, (c) regional economic impact analyses, and (d) an estimate of the per-unit cost of
water saved over a 50-year planning horizon (2009 through 2058). The model ArundoEcon© is
used to perform a baseline deterministic analyses using low- and high-value irrigated composite
acre values. That is, the saved water is initially valued based on being applied to agriculture as
irrigation. Since the actual crop mix irrigated with the saved water is unknown, a range is
provided by assuming all irrigated crops are “low-value,” and then again by including both “lowvalue”
and “high-value” irrigated crops.
Results of the water amount saved are 2/9 of the amount consumed, or approximately one acrefoot
of water for each acre of Arundo. For each acre-foot of water saved, 1.85 dryland acres can
be converted to low-value crop acres, and 0.71 can be converted to high-value crop acres.
Regional economic results indicate a present value of farm-level benefits ranging from $98 to
$160 million. Benefit-cost ratios are calculated with normalized prices and indicate a range from
4.38 to 8.81. Sensitivity analyses provide a robust set of results for Arundo agricultural water
use, effectiveness of control agents, replacement species’ water use, Arundo expansion rate after
control, value of water, and the cost of the program.
The pre-production processes and farm-gate economic impact analyses are estimated using
multipliers from the IMPLAN model. Regional results reveal a range of $9 to $18 million
annually in economic output and 197 to 351 jobs associated with the increase in gross revenues
due to the control of Arundo donax for the year 2025. Values for other select years are also
provided. Further results suggest a life-cycle cost per acre-foot of water saved of $44. This
amount is comparable to other projects designed to conserve water in the region.
The USDA)ARS, Weslaco, Texas Arundo donax biological control project will realize positive
results as indicated by the benefit-cost ratios, economic impact analyses, and competitive results
for the per-unit cost of saving water. These results indicate this project will have positive
economic implications for the U.S. and the Texas Lower Rio Grande Valley.
Collections
Citation
Seawright, Emily; Rister, M. Edward; Lacewell, Ronald; McCorkle, Dean; Sturdivant, Allen; Goolsby, John; Yang, Chenghai; Harris, B.L. (2009). Economic Implications of Biological Control
of Arundo donax in the
Texas Rio Grande Basin. Texas Water Resources Institute. Available electronically from https : / /hdl .handle .net /1969 .1 /90521.