Degradacja powierzchni ziemi – zakres terminologiczny, metody oceny i perspektywy badań = Land degradation – definitions, methods and research perspectives

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W artykule zwrócono uwagę na rosnące zainteresowanie problemem degradacji powierzchni ziemi w związku z obecną i przewidywaną w przyszłości dużą presją na zasoby środowiska przyrodniczego. Dokonano przeglądu definicji degradacji i jej postrzegania z punktu widzenia różnych dyscyplin naukowych. Zaprezentowano przykładowe metody identyfikacji i oceny degradacji w różnych skalach czasowo-przestrzennych, wskazując ich zalety i ograniczenia. Ponadto przedstawiono perspektywy badań degradacji powierzchni ziemi, wykazując konieczność rozwoju prac nad identyfikacją czynników degradacji i ich wzajemnego oddziaływania w strefie umiarkowanej na poziomie regionu i kraju. W tym kontekście szczególnie interesująca wydaje się możliwość połączenia oceny degradacji ziemi z oceną świadczenia usług ekosystemowych.

The analysis of the Scopus bibliographic database indicates a doubling of the frequency of use of the term land degradation in scientific articles from 302 to 658 times between 2010 and 2018. Most often it was used in publications in the fields of environmental, agricultural, biological, social and earth sciences, respectively. The growing interest in land degradation reflects expected population growth and the consequent increasing pressure on the natural environment on a global scale, with it at the same time being difficult to predict the effects of extreme events due to climate change. The purpose of the article is to review the definition of land degradation from the point of view of various scientific disciplines, and to draw attention to the methods of identification and assessment of land degradation, as well as research perspectives. The review of definitions indicates that land degradation is a complex concept lacking a single identifying feature. It describes how natural resources (soil, water, vegetation, rocks, air and topography) are depleted or experience a lowering in quality. Although a precise definition of the concept of degradation is not possible, due to the existence of many factors responsible for it, land degradation is by definition not merely an environmental problem, but also a social once. The diverse range of land degradation concepts results in difficulties with the development of methodology and the supply of comparable information. The choice of identification method and degradation assessment, next to the purpose of the study, depends on the latter’s spatial scale. At detailed scales, over areas of up to approx. 100 km2 (e.g. a small catchment), expert knowledge is most often used in conjunction with field survey and the analysis of cartographic and remote-sensing data. In the assessment of land degradation on a medium scale (that of a region or country), a desertification and land-use analysis developed for the Mediterranean region – MEDALUS (Mediterranean Desertification and Land Use) is often used. It takes into account the values of several physical variables, including climate characteristics, soil features, vegetation and anthropogenic factors, including land use with the forms of environmental protection. MEDALUS is a stable degradation assessment procedure, verified in many European countries, including Central Europe, North Africa, the Middle East, as well as China’s subtropical zone. Only four approaches have so far been used to assess degradation on a global scale. All studies were based on proxy data in the form of degradation indicators derived from expert studies at various scales, satellite observations, biophysical models and the inventorying of abandoned farmland. The presented definitions, research methods and results of studies on degradation indicate that there are still serious deficiencies with the identification of degradation factors and the study of their interactions, especially at regional and national levels. The gathering together of many local expert studies into unified databases should facilitate transition to analysis at the level of large physico-geographical regions and countries. In this context, the possibility of an assessment of land degradation being combined with one relating to the provisioning of ecosystem services would seem particularly interesting.