Ulf Helldén

• PhD, Professor emeritus
• Lund University

Drylands comprise one-third of the Earth’s land area. They pose research, management, and policy challenges impacting the livelihoods of 2.5 billion people. Desertification is said to affect some 10-20% of the drylands and is assumed to expand with climate change and population growth. Recent paradigms stress the importance of understanding linkage...

This paper presents the development of a system dynamic model to simulate and analyze desertification.The human–environment coupled model integrates socio-economic drivers with bio-physical drivers of biomass production, land degradation and desertification. It is based on the UN and GEF definitions of desertification. It illustrates the concept of...

The paper presents results on the use of NOAA AVHRR data for desertification monitoring on a regional–global level. It is based on processing of the GIMMS 8 km global NDVI data set. Time series of annually integrated and standardized annual NDVI anomalies were generated and compared with a corresponding rainfall data set (1981–2003).The regions stu...

The word "desertification" was introduced in 1949 b y the French scientist Aubreville in his report "Climats, forêts et désertification de lAfrique tropicale". The concept, however, was discussed earlier by European and American scientists in terms of increased sand movements, desiccation, desert and S ahara encroachment and man made deserts. Deser...

A study of aerial photography from 1962 and satellite data from later periods did not indicate any evidence for a continuous Sahara desert movement southwards, large shifts in land system borders, southward sand and dune complex encroachment or systematic growth of village “desert patches”. A study of the potential of a transformed normalized diffe...

The possible use of LANDSAT imagery and digital data for monitoring desertification indicators in Tunisia was studied. Field data were sampled in Tunisia for estimation of mapping accuracy in maps generated through interpretation of LANDSAT false color composites and processing of LANDSAT computer compatible tapes respectively. Temporal change stud...

Spectral diagrams, illustrating the spectral characteristics of different water types, were constructed by means of simple statistical analysis of the various reflectance properties of water areas in Southern Scandinavia as registered by LANDSAT-1. There were indications that water whose spectral reproduction is dominated by chlorophyllous matter (...

The possibilities of using LANDSAT-1 images for environmental studies, with special references to water quality studies, were investigated by selecting test areas in southern Scandinavia. The MSS images of different bands are compared under the magnification of an Interpretoscope and densitometric analyses are performed in a Schnell-photometer. The...

In order to investigate the possibility of using ERTS 1 MSS images for environmental studies with special reference to water quality studies and (and use mapping, test areas in South and Middle Sweden and adjoining water areas have been selected. MSS images of different bands are compared under the magnification of the Interpretoscope (Zeiss Jena)....