Jeremy F. Wallace

Assessing landscape health by scaling with remote sensing : when is it not enough?

Assessment of the health of landscapes, by monitoring their condition over space and time, is needed to better understand the processes for sustaining or, in many cases, repairing them. Remote sensing is a tool that can efficiently identify and assess areas of landscape damage at different scales and help land managers solve specific problems. Remote sensing may appear to be a panacea for all monitoring situations but sometimes the information it provides is not enough by itself. In this paper we give examples of both scenarios—when remote sensing alone is adequate and when it is not. When remotely sensed data alone is not sufficient, monitoring problems can be solved by incorporating additional finer scale data. We use a five-step procedure based on scaling to help land managers answer the question: when is remote sensing data alone not sufficient to underpin the information needs required to achieve a specific management goal?

Spectral discrimination and mapping of waterlogged cereal crops in Western Australia

Abstract Abstract. A study was conducted in Western Australia to determine whether remotely-sensed spectral data can be used to detect and map areas in cereal crops where growth has been affected by waterlogging, Spectral discrimination was established between waterlogged and non-waterlogged crop using either 13-band airborne MSS data or Landsat-TM data. Near infrared and thermal channels were found to be important in providing the observed discrimination. Classification procedures incorporating measures of confidence of class membership were applied, and produced classification maps which agreed closely with ground information, It is concluded that timely Landsal-TM data, together with ground calibration information, can be used for mapping and monitoring waterlogged cereal crops.

A BRDF-corrected Landsat 7 mosaic of the Australian continent

Landsat TM imagery is being used to monitor landcover change in a number of operational projects in Australia. Most recently, the Australian Greenhouse Office (AGO) has undertaken a project to provide historical monitoring of changes in woody vegetation across the continent. In order to map and monitor landcover changes in a consistent and comparable manner across broad areas, it is highly desirable to have a consistently calibrated numerical base. To this end, the AGO has supported the creation of a rectification and calibration base for Australia, using Landsat TM data; 369 Landsat 7 images from the period July 1999 to September 2000 were purchased from the Australian Centre for Remote Sensing (ACRES). This paper describes the processing and production of the calibration base from these images.

Monitoring native vegetation on an urban groundwater supply mound using airborne digital imagery

High spatial resolution airborne imagery has been acquired at anniversary dates and processed to produce monitoring information for vegetation on the Gnangara Mound. The Mound, located north of Perth Western Australia, is of great importance to the citys water supply and retains significant biodiversity values. An effective monitoring system for vegetation is a priority for multiple agencies concerned with management and regulation of the Mound. Individual tree deaths and spatial patterns across the area were detected using the image sequences. Spatial analysis showed no associations with borefield pumping, but active disease processes were identified. Methods and results are presented.

Mapping and monitoring land use and condition change in the southwest of Western Australia using remote sensing and other data

In the south-west of Western Australia, the clearing of land for agricultural production has lead to rising saline ground water, resulting in the loss of previously productive land to salinity; damage to buildings, roads and other infrastructure; the decline in pockets of remnant vegetation and biodiversity; and the reduction in water quality. The region in question comprises some 24 million hectares of land. This has resulted in a wide variety of stakeholders requesting quantitative information regarding historical, present and future trends in land condition and use. Historically, two methods have been widely used to obtain information: (1) surveys requesting land managers to provide estimates of land use and condition; and (2) human interpretation of aerial photography. Data obtained from the first approach has in the past been incomplete, inaccurate and non-spatial. The second approach is relatively expensive and as a result is incomplete and is not regularly updated.In this paper, we describe an approach to land use/condition monitoring using remotely sensed and other data such as digital elevation models (DEMs). We outline our methodology and give examples of mapping and monitoring change in woody vegetation and salinity.

Mangrove monitoring using sequences of Landsat imagery in the Mary River wetlands

Mangroves have expanded in the Mary River wetlands in the Northern Territory of Australia due to the widening and headward extension of tidal channels as a result of saltwater intrusion. Approximately 240 km/sup 2/ of freshwater wetlands have been altered over the past 50 years, with further alteration anticipated. A mangrove monitoring method has been implemented based on summaries of change in a greenness index from a time series of calibrated Landsat TM/ETM imagery covering the years 1987-2000. Field verification was carried out in 2000. Results indicate that this method can be used to detect the extent and rate of mangrove expansion in these wetlands over the past decade. It has been estimated that over 100 km of mangroves have been established on tidal creek extensions during this period. These results not only offer further insight into the environmental processes occurring in this region but also demonstrate the value of temporal datasets for deducing changes in land use and associated impacts.

Evaluation of CBERS Image Data: Geometric and Radiometric Aspects

In Australia, Landsat imagery is currently used in a number of regional and national monitoring projects. However, the future of Landsat imagery is not assured. Both Landsat 5 and Landsat 7 are estimated to run out of fuel around 2010. With the looming gap in Landsat data continuity it is timely to consider the issues involved in using data from other sensors to continue these monitoring programs. In the context of the Australian Greenhouse Office (AGO) Land Cover Change Program (LCCP) (http://www.climatechange.gov.au/ncas), this paper describes the issues on CBERS geometric and radiometric aspects, and quantifies the effects of using CBERS images to produce forest cover maps. Other alternatives to Landsat data that are being considered by AGO are SPOT 4 and Landsat 7 SLC-off images (Furby and Wu 2006a) and the Indian Remote Sensing satellites (IRS) (Furbyand Wu 2006b).

Environmental Monitoring Using a Time Series of Satellite Images and Other Spatial Data Sets

As a result of extensive farmland clearing over the last hundred years or so, dry-land salinity is a major problem in Western Australia. In fact, in some parts of the state, over 20 percent of Agricultural land is no longer productive. Prior to the work to be described in this chapter, no reliable large scale estimates of the extent or progression of salinity were available. This chapter describes a methodology for monitoring the historical extent of salinity, using a time series of satellite imagery, landform information derived from digital elevation models and ground truth data collected by experts with local knowledge. This work has served to highlight the salinity problem to decision makers in government and to provide input into the process of developing and applying remedial measures to arrest the spread of salinity.

Forest vegetation monitoring and runoff in water supply catchments affected by drying climate

The south-west of Western Australia has experienced reduced rainfall over recent decades. Annual rainfall in the states capital city, Perth, has declined by approximately 20% since the 1970s. Runoff from the forested catchments into the citys water supply dams has declined more dramatically — of the order of 50%. Forest vegetation plays a major role in catchment water balance. Thinning of forest cover has been proposed as a means to increase catchment yields, and a trial is being conducted. Time series Landsat imagery provides information on historic forest disturbance on all catchments and an alternative data integration analysis combining these indicators with historical rainfall and runoff data is being conducted to estimate effects of forest thinning on catchment runoff under different rainfall scenarios. The remote sensing analysis has provided indication of forest adaption to the drying climate. These results and a sample of the hydrological data and analysis are presented in this paper.

Recent development in vegetation monitoring products from Australia's National Carbon Accounting System

Australias National Carbon Accounting System Land Cover Change Program (NCAS-LCCP) has been developed over the past decade to provide fine-scale monitoring of forest land cover changes for the continent, and to estimate greenhouse gas (GHG) emissions from land use and land use changes. Time series Landsat coverages of the continent are processed to provide the monitoring component of the system. Forest extent and change products were the initial priority and have been routinely produced since 2002. Since then, a number of other monitoring products have been trialled and developed based on the NCAS-LCCP image archives, including the Woody Vegetation Trends described here. This product has been produced nationally within forested areas, providing indicators of changing forest density and degradation relevant to GHG accounting, and also to conservation and natural resource management.