Richard A. Wadsworth

Land cover change in Europe between 1950 and 2000 determined employing aerial photography.

BIOPRESS (‘Linking Pan-European Land Cover Change to Pressures on Biodiversity’), a European Commission funded ‘Global Monitoring for Environment and Security’ project, produced land cover change information (1950—2000) for Europe from aerial photographs and tested the suitability of this for monitoring habitats and biodiversity. The methods and results related to the land cover change work are summarized. Changes in land cover were established through 73 window and 59 transect samples distributed across Europe. Although the sample size was too small and biased to fully represent the spatial variability observed in Europe, the work highlighted the importance of method consistency, the choice of nomenclature and spatial scale. The results suggest different processes are taking place in different parts of Europe: the Boreal and Alpine regions are dominated by forest management; abandonment and intensification are mainly encountered in the Mediterranean; urbanization and drainage are more characteristic of the Continental and Atlantic regions.

What is land cover

Much geographic information is an interpretation of reality and it is possible for multiple interpretations to coexist. This is unproblematic for the research community but, as the numbers of users increase through initiatives resulting in data integration on an unprecedented scale, such as E-science and GRID, issues of information meaning and conceptualisation become more important. We explore these issues through the mapping of land cover and the variety of conceptions of land-cover features that may be held by actors in the creation, distribution, and use of the information. Current metadata do not report the wider meaning of the information categories in terms of the decisions that were made and by whom in specifying class conceptualisations.

Landscape metrics with ecotones: pattern under uncertainty

Landscape metrics are in widespread use, but previous research has highlighted problems over scale and error in the reliability of the metric values. This paper explores the variation of metric values when it is hard to distinguish exactly where one land cover type changes into another; when the ecotone is not an abrupt transition, but has a spatial extent in its own right. The values of metrics are explored in a landscape classified, using satellite imagery and the fuzzy c-means classifier, into fuzzy sets so that every location has a degree of belonging to all classes. The result is that any ecotone can be characterised by a variety of metric values depending on the degree to which a location is in any particular land cover class. The values recorded show some similarities, however, to those for an interpretation of the same landscape with abrupt changes, but the nature of that similarity varies unpredictably between metrics and classes. This analysis provides a limited degree of reassurance for those using metric analysis where the boundaries may have spatial extent, but much further work is required to establish an improved description of metrics under this condition.

Integrating land-cover data with different ontologies: identifying change from inconsistency

Spatially coincident land-cover information frequently varies due to technological and political variations. This is especially problematic for time-series analyses. We present an approach using expert expressions of how the semantics of different datasets relate to integrating temporal time series land-cover information where the classification classes have fundamentally changed. We use land-cover mapping in the UK (LCMGB and LCM2000) as example data sets because of the extensive object-based meta-data in the LCM2000. Inconsistencies between the two datasets can arise from random, gross and systematic error and from an actual change in land cover. Locales of possible land-cover change are inferred by comparing characterizations derived from the semantic relations and meta-data. Field visits showed errors of omission to be 21% and errors of commission to be 28%, despite the accuracy limitations of the land-cover information when compared with the field survey component of the Countryside Survey 2000.

Detecting change in vague interpretations of landscapes

Abstract For a number of years researchers have advocated the use of fuzzy classifications in the study of land cover mapping from satellite imagery. Some studies have looked at the change of fuzzy spatial object, but none have considered the direct corollary of the so-called change detection matrix. In this paper we discuss populating the fuzzy change matrix, using fuzzy logic statements. Intersection is the principal operation, but it is argued that the Bounded Difference is the intersection operation for which the results make sense for determining loss and gain of a cover type. While the minimum operator works in actually populating the matrix. An alternative matrix can be generated using just the Bounded Difference. The detection of ecotones and the analysis of ecotone change are also discussed. It is suggested that the mappings derived express subtle variations in land cover types and change in those types as well as in ecotones, which may be related more conclusively to an ecological process than are Boolean mappings with associated linear boundaries.

Actor–network theory: a suitable framework to understand how land cover mapping projects develop?

Abstract The Countryside Surveys of 1990 and 2000 are introduced and their methodological or ontological differences described. Actor–network theory examines the processes by which individual scientific claims are supported, debated and constructed by determining the interactions, connections and activities of the actors involved. The actors and their networks for the Countryside Surveys of 1990 and 2000 are compared. Such an analysis provides a description of why science evolves. Changes in the commissioning context behind scientific results and the process by which empirical facts are established are clearly illustrated. This type of analysis goes beyond the technological developments that would be revealed if only the scientific elements were examined. This type of analysis provides a useful tool to those seeking to reconcile ontological and semantic differences between scientific data.

The use of airborne remote sensing for extensive mapping of intertidal sediments and saltmarshes in eastern England

Airborne remote sensing with a Compact Airborne Spectrographic Imager (CASI) and a Daedalus Airborne Thematic Mapper (ATM) has been used to map sediment types and biotic associations for the intertidal zone along 270 km of coastline from the Humber Estuary to North Norfolk, UK within the LOIS BIOTA (Land-Ocean Interaction Study, Biological Influences On interTidal Areas) programme. This allows field-based biotic and sedimentary information to be extrapolated to provide information for modelling the coastal processes of erosion and accretion. The method adopted for image classification was unsupervised clustering which was used to map an extensive area (476 km 2 ) of the exposed intertidal zone at a spatial resolution of 5 2 5 m pixels. Ten broad classes of intertidal sediments and vegetation have been mapped with approximately 70% correspondence with ground data.

Assessment of a Semantic Statistical Approach to Detecting Land Cover Change Using Inconsistent Data Sets

A semantic, statistical approach to reconciling data with different ontologies is introduced. It was applied to UK land cover datasets from 1990 and 2000 in order to identify land cover change. The approach combined expression of expert opinion about how the semantics of the two datasets relate with spectral homogeneity metadata. A sample of the changes identified was assessed by field validation. Change was identified in 41 percent of the visited parcels, and all of the false positives were found to be due to classification error in either dataset. Thus, the approach reliably identifies inconsistency between two datasets, and the results indicate the suitability of uncertainty formalisms. The inclusion of extensive objectlevel metadata by the data producers greatly facilitates practical solutions to problems of data interoperability.

Short-term vegetation succession and erosion identified by airborne remote sensing of Westerschelde salt marshes, The Netherlands

The Westerschelde estuary is the only major uncontrolled estuary in the south of The Netherlands. More than 15 000 ships per year use it to access the Belgian port of Antwerp. A major dredging operation along the Westerschelde in the late 1990s has changed the tidal regime and increased tidal inundation of the salt marshes at high tide. Airborne remote sensing (CASI) has been acquired in 1998 and 2000 for three salt marsh sites in the Westerschelde estuary. An additional dataset exists for one site for 1993. The CASI data have been classified into maps of salt marsh vegetation. These provide an input for GIS-based modelling of sediment erosion/accretion. Maps of Normalized Difference Vegetation Index (NDVI) values allow change detection: successional change of salt marsh vegetation is clearly demonstrated. The 1993, 1998 and 2000 data show a successional trend between 1993 and 1998 that is, in part, reversing between 1998 and 2000. Data also showed significant erosion of the salt marsh edge. Data are being used to extrapolate field measurements and help produce sediment budgets for the individual salt marshes.

Using semantics to clarify the conceptual confusion between land cover and land use: the example of ‘forest’

This article is concerned with data and classifications that confuse the concepts of land cover and land use. This conceptual confusion is problematic for data integration and has resulted in calls for the separation of land use and land cover from the global land monitoring community (GLP 2005). Text mining is used to unravel the different concepts embedded in land cover and land use semantics and applied to legal definitions of forest cover and use. Whilst the results show the distinct biological dimension to land cover descriptions and the socioeconomic character of land use, they reveal the deep degree of semantic confusion embedded in land cover and land use descriptions. The implications for this lack of internal semantic accuracy and consistency in land resource inventories are discussed and the case made for separating the concepts of land cover from land use.