Charles F. Hutchinson

Measuring the effect of overgrazing in the Sonoran Desert

Long term overgrazing in Mexico has caused a sharp discontinuity in vegetative cover along the international border in the semi-arid Sonoran Desert. The United States side, protected from overgrazing by the Taylor Act since 1934, exhibits longer, more plentiful grasses and less bare soil than adjoining Mexican lands. Satellite- and ground-based datasets were used in a multi-scale examination of the differential radiative and reflective characteristics of the two regimes. The more exposed Mexican landscape dries more rapidly than the United States following summer convective precipitation. After about three days, depletion of soil moisture evokes a period of higher surface and air temperatures in Mexico. Good correspondence was found between remote and in situ measures of surface temperature and biomass.

Guidelines for demonstrating geographical information systems based on participatory development

Abstract The transfer of GIS technology has not met with uniform success in lesser-developed countries. It has been argued that this may be due to many efforts being technology-driven rather than demand-driven. In agricultural development, technology is transferred through a demand-driven participatory approach which incorporates the ultimate recipients of the technology in the design, implementation and evaluation of projects. A project to demonstrate the use of GIS technology for wasteland development in India involving seven Indian research institutes was undertaken by the U.S. Agency for International Development. In the Indian GIS demonstration, technical approaches proposed by each institute were largely technology-driven. To counter this tendency, a set of evaluation criteria or guidelines based on the participatory approach was developed to refine proposals.

Indicators of rangeland change and their potential for remote sensing

Selected environmental variables were evaluated for their utility as indicators of rangeland change and their potential for remote sensing. Fifty-nine study sites were sampled in southern New Mexico. Total vegetation cover and the ratio of shrub cover to grass cover were related to disturbance. Increasing degrees of change were associated with a decrease in total vegetation cover, an increase in the ratio of shrub to grass cover and a decrease in organic soil cover (litter and algal crusts). Total vegetation cover and organic soil cover can be monitored from single-date satellite data, but total vegetation cover alone may provide ambiguous results. The ratio of shrub to grass cover, which is necessary to identify the direction of change can be determined by examining multi-date satellite data that correspond to the times when grasses and shrubs exhibit their maximum green biomass.

Land use vs. climate as causes of vegetation change: a study in SE Arizona

Abstract Research and discussion regarding the causes of historic vegetation change are important to potential policies and prescriptions for addressing problems related to environmental change. This paper examines the case of southeastern Arizona where significant historic vegetation change has occurred. Using repeat aerial photography covering a period of approximately 50 years, the analysis considers the two primary hypotheses for vegetation change in the region: climate, and land use. Subsequent to a brief review of these hypotheses and the methods employed to explore them, the paper looks at two sites in Arizona and analyzes the direction and cause of vegetation change. From both this analysis and a description of historical land uses in the area, evidence is presented that land use and not climate change is the primary driver of historical vegetation in the areas.

A comparison of greenness measures in two semi-arid grasslands

A field experiment was conducted during 1988 in a semi-arid grassland along a portion of the U.S./Mexico border in which the utility of NDVI-transformed data for estimating green vegetation amount and cover was explored. Results showed that, although there was significant difference in green and total biomass between the U.S. and Mexico sites, we were unable to find any correlation between either these vegetation parameters and NDVI values calculated from reflectance measurements. Based on these results, it would appear that semi-arid perennial grasslands can pose problems for remote sensing analysis due to their erectophile structure, the likelihood of significant accumulation of senescent biomass, and dominance of soil background in sparsely vegetated areas. Therefore, if remotely-sensed data, and indices derived from them, are to be used in global change models, it is critical to establish if these indices are sufficiently sensitive to distinguish long-term change from the seasonal and spatial variability in vegetation biomass normally found within these perennial grassland communities.

The use of large-scale aerial photography to inventory and monitor arid rangeland vegetation

Interpretation of large-scale color infrared and color aerial photography can be a labor- and cost-effective means to make inventory of and monitor rangelands while maintaining accuracy. Ground measurements of total vegetation cover, tree, shrub and cacti cover at Organ Pipe Cactus National Monument were taken in 1975 and 1984. Estimates of ground vegetation cover made using large scale (1:1200) color and color infrared aerial photography were compared to these ground measurements. High correlation coefficient values exist between color infrared transparency estimates and ground measurements of total vegetation cover (r = 0.972) and shrub cover (r = 0.891). Correlation coefficients were similarly high when matching color prints against ground measurements of total cover (0-976) and shrub cover (0.858). Estimates from color infrared film transparencies corresponded better with ground measurements for both tree and cactus cover, with r values of 0.685 and 0-812 respectively, than the estimates from color print photographs with r values of 0.501 for tree cover and 0.246 for cactus cover.

The impact of historic fuelwood cutting on the semidesert woodlands of southeastern Arizona.

D uring the past century, major vegetation changes have occurred in the semidesert lands of southeastern Arizona. Among the changes have been the elimination of many native riparian forests, the introduction of vigorous exotics, local expansion of some natives, clearing of vast areas of scrub desert, modification of the composition of grasslands, alterations in regional fire ecology, and major structural changes in the woodlands. These changes usually are attributed to climatic shifts, cycles in rodent populations, grazing, groundwater withdrawal, and fire suppression.1 Despite the significance of these agents, the effects of most historic land uses on the vegetation have not been completely identified, nor have the land uses themselves been subjected to detailed analysis. This is remarkable, since most of the documented vegetation changes have occurred in the past one hundred years, the period of greatest influx of Anglo-Americans into the region. From a wide range of historic land-use activities that have modified the vegetation, such as grazing, agricultural clearing, woodcutting, groundwater withdrawal, urban de-

Old and New: Changing Paradigms in Arid Lands Water Management

Water management paradigms and practices have evolved markedly from the post-World War II years to the twenty-first century. Changes have been particularly urgent and visible in water-limited arid lands. Notable trends include movement from an emphasis on technological, supply-side solutions toward sociological, demand-side management; from rigid top-down state control toward decentralized management; and from local or regional management arenas toward integrated, multilateral formation of water policy from a global perspective. Efforts continue to augment water supplies, but practice has shifted from tactics such as weather modification to energy-efficient desalination, wastewater reuse and, significantly, conservation, which was hardly considered in previous periods of perceived abundance. Overtaking even these efforts in importance is a growing intellectual elaboration of an integrated water management paradigm, which recognizes that each element on both the supply and demand sides of the equation contributes to the total water availability and requires consideration of linkages between urban and rural water use as well as between the domestic, industrial, and agricultural sectors. This awareness has spurred the establishment of “global water initiatives,” marking a shift toward globalization of water management to achieve higher levels of integration.

Informing the elk debate: applying NASA Earth Observing System (EOS) data to natural resource management conflicts in the western states

This study was designed to provide information that might help resource managers understand the distribution of elk in Arizona as a consequence of seasonal variation and in response to extreme climatic events (i.e. El Nino and La Nina). The first task involved modeling elk populations over time. A technique for modeling the elk population has been developed that is based on harvest data, gender ratios, and estimates of male mortality. This provided estimates of elk populations for individual game management units (areas for which harvest is reported and within which elk are managed by the Arizona Game and Fish Department). The second task involved the use of satellite data to characterize vegetation responses to seasonal and interannual climate variation among vegetation associations within game management units. This involved the use of NOAA-AVHRR time series data to describe temporal vegetation behavior, Landsat data to describe spatial vegetation distribution in conjunction with U.S. Forest Service vegetation maps. Elk population estimates were correlated with satellite-derived vegetation measures by vegetation association through time. The patterns of elk distribution that this revealed were complex. Not surprisingly, animals appear to respond to differences in vegetation availability-both seasonally and interannually-as portrayed by satellite data.

Land remote sensing technology and methodology

Remote sensing is a tool for gathering information about the Earths surface and monitoring how it changes. A large number of remote sensing systems have been developed that exploit different parts of the electromagnetic spectrum and that produce data in different formats at varying scales and costs. These data may be acquired for virtually any place on Earth. A body of manual and automated techniques have evolved for processing and interpreting remote sensing data. The selections of a remote sensing system and of the techniques by which data are processed are driven by information requirements of varying detail and constrained by cost.