A Remote Sensing and GIS-based model of avian species habitat and its potential as a part of an environmental monitoring programme

Dissertation / Doktorarbeit von Thomas Gottschalk

Introduction:

Over 10% (1186 species) of the bird species in the world are threatened with extinction in the near future, almost all of them due to habitat change or loss by man. Likewise, 1130 mammals, 296 reptiles, 146 amphibians and 5611 plants have been identified as endangered species. The destruction of natural habitat is the major factor contributing to the global species extinction event. The increasing loss of biodiversity has centred on conducting inventories and monitoring species and habitats, especially in identifying areas of high species richness, threatened species and species of restricted or local distribution. In 1992 the UNCED-Conference in Rio de Janeiro pointed out the need for monitoring the environment, leading to the Convention on Biological Diversity and the Agenda 21. Article 7 of the Convention on Biological Diversity deals with identification and monitoring, which are to be undertaken with sampling and other techniques. New methodologies with a view to undertaking systematic sampling and evaluation of the components of biological diversity are to be developed.

While the number of identified threatened species has increased dramatically, a huge gap in knowledge of ecosystems and their fauna and flora remains. Distribution, status and ecology of species are mostly unknown in many countries, as is the degree they are endangered. In view of the immense unknown ecosystems in the world, a great number of which are located in developing countries, conventional survey and mapping methods cannot deliver the necessary information in a timely and cost-effective fashion. Nature conservation will require large volumes of Remote Sensing (RS) data if the quality of planning is to improve. With RS technology, we may be able to make real progress in understanding why more species occur in some places than in others and in identifying the most critical places that must be protected to preserve the maximum number of species into the 22nd century and beyond. As current air photos are often not available, satellite images are the sole source of data for many regions of the world.

Fortunately, computer technology has improved enormously in the last years, mainly processing time, storage requirements as well as programme features and possibilities. Concurrent declining costs of computer hardware have favoured the design of new techniques for special data processing and combining remotely sensed information with other extensive data sources.

In the last 20 years Geographic Information Systems (GIS) have been widely accepted and used as a tool for a host of applications in planning processes, in storing, analysing and maintaining data. Ground survey information together with RS imagery by using GIS techniques offers a huge potential for quick identification of areas of high biodiversity.

The approach of this study is to combine the potential of bird data, GIS and satellite-based RS in view of using these components to monitor the environment. After defining the terms monitoring and habitat in chapter 1.1, chapter 1.2 to 1.4 mainly focus on the potential using GIS, bird and satellite data. Chapter 1.5 continues with a detailed literature review of previous studies, which used GIS, bird and satellite image data to focus attention on issues considered to be the most important for effective use of the three components. Therefore, the main characteristics, especially methodology, satellites image analysis, bird census, scale and accuracy requirements were analysed and compared. Chapter 1.6 focuses on weaknesses of these studies and specifies objectives for the present study corresponding to the weaknesses.

Definition of monitoring and habitat:

As the two terms monitoring and habitat are widely used in this study precise definitions are given in the following.

Monitoring:

Monitoring has become more and more important in assessing nature and its natural and human-induced changes. It is a very important information-tool for decision-making in conservation policy. The term monitoring has been defined by several authors. DRÖSCHMEISTER favours the following definition of HELLAWELL, as it is the most useful and the most unambiguous one: „Monitoring - Intermittent (regular or irregular) surveillance carried out in order to ascertain the extent of compliance with a predetermined standard or the degree of deviation from an expected norm”.

The use of biological monitoring (for example birds as biotic key indicators) in addition to non-biological monitoring (for example measurements of physical parameters) has the advantage of disclosing reactions of living organisms to environmental changes, which may otherwise be left undiscovered. Monitoring merely by non-biological methods has the disadvantage of its specificity on single environmental variables and often of its higher frequency of sampling occasions, which may not include significant events. Biomonitors are usually selected to complement physical monitoring, but in some instances provide the only available means of monitoring.

Table of Contents::

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Chapter 5.1.2, Spatial scale:

Scaling issues are fundamental to all ecological investigations. To define the proper geographic scale is one of the main problems when conducting research on species-environment relationships and when monitoring the environment. LEVIN pointed out that there is no single correct scale with which to evaluate ecosystems. The exact choice of scale depends on specific study objectives. Species habitats may be defined broadly (as ecological zones or biomes) or narrowly (as habitats in the usual sense, or even more narrowly as sub-habitats or microhabitats). If the scale of the study and analysis is not tailored to the species and questions to be dealt with, key influences on habitat selection may be overseen by the researcher. Furthermore, it is not easy to determine the proper scale (or length of habitat spectrum) as species show different relationships in analyses conducted for example at continental and at regional levels. On a large scale, between-habitat level of analysis birds may respond to some elements of general habitat configuration, but their within-habitat responses may be more strongly associated with details of habitat floristic. PRIBIL and PICMAN showed that for habitat selection by birds the same factor could be insignificant on a broad scale (choice of nesting areas within a habitat) but important on a narrow scale (choice of a nest side within a nesting area). The question that is still open is how to identify the minimum resolution of landscape data that is sufficient for a given purpose. According to MORRISON plant taxonomy becomes increasingly important, as studies become increasingly site-specific. They suggest viewing habitat analysis first from the broadest scale, working down to the finest level of scale necessary to answer the question of interest.

In GARSHELIS the spatial scale at which habitats are viewed is discussed in detail. The number of habitats taken into consideration can directly affect the results. When too many types are defined, number of points per habitat type decrease, thereby diminishing the power of the statistical tests to distinguish differences between use and availability. But the criteria used to partition types may affect results and not just the number of types. In the present study, the comparison of the number of significances between bird species occurrence and the accumulated remotely sensed habitat types as well as bird species occurrence and the more detailed classified habitat types show that habitat specification and the level of habitat classification is of major importance for the description of habitat preferences on birds tested the effects of coarser spatial resolution of a satellite-based habitat map. To do so, they eliminated polygons that are less than 20ha and observed no significant effects on a habitat suitability model for the California Condor Gymnogyps californianus.

A higher number of significant relationships would be calculated if the study area were larger and parts of the tall grasslands or of the wooded areas of SNP were included in the analyses. An increase in size would incorporate greater spatial heterogeneity, as a greater variety of habitat types would be included in the area being studied. Along with the increase of significant relationships, a more distinct pattern of species distribution would also be visible.

As mentioned above, specific features such as narrow linear grooves, hedgerows, fences and small patches of land or single trees cannot be identified exactly in many satellite images, but they may be of importance for specific bird species. These features have to be identified and mapped by ground survey or by specific image analysis techniques such as contextual analysis or edge detection.