Evaluation and selection of indicators for land degradation and desertification monitoring : methodological approach

International audienceAn approach to derive relationships for defining land degradation and desertification risk and developing appropriate tools for assessing the effectiveness of the various land management practices using indicators is presented in the present paper. In order to investigate which indicators are most effective in assessing the level of desertification risk, a total of 70 candidate indicators was selected providing information for the biophysical environment , socioeconomic conditions, and land management characteristics. The indicators were defined in 1,672 field sites located in 17 study areas in the Mediterranean region, Eastern Europe, Latin America, Africa, and Asia. Based on an existing geo-referenced database, classes were designated for each indicator and a sensitivity score todesertification was assigned to each class based on existing research. The obtained data were analyzed for the various processes of land degradation at farm level. The derived methodology was assessed using independent indicators, such as the measured soil erosion rate, and the organic matter content of the soil. Based on regression analyses, the collected indicator set can be reduced to a number of effective indicators ranging from 8 to 17 in the various processes of land degradation. Among the most important indicators identified as affecting land degradation and desertification risk were rain seasonality, slope gradient,plant cover, rate of land abandonment, land-use intensity, and the level of policy implementation

CONTRIBUTION OF EMPIRICAL METHODS AND SATELLITE DATA USE FOR ESTIMATING DAILY REFERENCE EVAPOTRANSPIRATION

Στην παρούσα εργασία χρησιμοποιούνται επίγεια και δορυφορικά μετεωρολογικά δεδομένα του έτους 2014 από την περιοχή της Βοιωτίας. Τα επίγεια δεδομένα προέρχονται από τον αυτόματο αγρομετεωρολογικό σταθμό (ΑΑΣ) μέτρησης της εξατμισοδιαπνοής αναφοράς (ΕΤο) του Γεωπονικού Πανεπιστημίου Αθηνών (ΓΠΑ). Τα μετεωρολογικά δορυφορικά δεδομένα (SAT) αντιστοιχούν σε πολύγωνο 0.25οΧ0.25ο εντός του οποίου λειτουργεί και ο ΑΑΣ. Χρησιμοποιώντας τα επίγεια αλλά και τα δορυφορικά δεδομένα, υπολογίσθηκε η ΕΤο με τη μέθοδο FAO-56 PM, αλλά και με τρεις εμπειρικές μεθόδους (Copais, Valiantzas και Hargreaves-Samani) και πραγματοποιήθηκαν συγκρίσεις με σκοπό να αξιολογηθεί η αξιοπιστία των μοντέλων. Ως βάση των συγκρίσεων υιοθετήθηκε η μέθοδος FAO-56 PM με χρήση επίγειων δεδομένων. Από την εργασία προκύπτει ότι τόσο για τα επίγεια όσο και για τα δορυφορικά δεδομένα η μέθοδος Copais δίνει τις καλύτερες εκτιμήσεις ακολουθούμενη από την μέθοδο Valiantzas και με σοβαρή υπερεκτίμηση η Hargreaves-Samani. In the present study we used ground and satellite meteorological data of the year 2014 from the region of Viotia-Greece. The ground data were obtained from the automatic grass reference evapotranspiration station (AAS) of the Agricultural University of Athens. The satellite data (SAT) cover an area of 0,25ο x 0,25ο that includes the AAS. By using the ground and the satellite data we calculated the reference evapotranspiration, ΕΤο, with the method FAO-56 PM and with three empirical methods (Copais, Valiantzas and Hargreaves-Samani). The FAO-56 PM was used as a benchmark method to compare and validate the performances of the others methods. The results show that for both the ground and the satellite data, Copais method is the most accurate followed by Valiantzas and Hargreaves-Samani, indicated by serious overestimation

An exploratory analysis of land abandonment drivers in areas prone to desertification

The abandonment of land is a global problemwith environmental and socioeconomic implications. An approach to assess the relationship between land abandonment and a large set of indicators was illustrated in the present study by using data collected in the framework of the European Union DESIRE research project from 808 field sites located in 10 study sites in the Mediterranean region, Eastern Europe, Latin America, Africa and Asia. A total of 48 indicators provided information for biophysical conditions and socioeconomic characteristics measured at the plot level. The selected indicators refer to farm characteristics (family status, land tenure, present and previous types of land-use, soil depth, slope gradient, tillage operations) and to site-specific characteristics including annual rainfall, rainfall seasonality and water availability. Classes were designated for each indicator and a sensitivity score was assigned to each class based on existing research or empirically assessing the importance of each indicator to the land abandonment issue. Questionnaires for each process of land degradation were prepared and datawere collected at field site level in collaboration with land users. Based on correlation statistics and multivariate analyses more than ten indicators out of 48 resulted as significant in affecting land abandonment in the studied field sites. Among them, the most important were rainfall seasonality, elderly index, land fragmentation, farm size, selected soil properties, and the level of policy implementation. Results contribute to the development of appropriate tools for assessing the effectiveness of land management practices for contrasting land abandonment

Exploring the Impact of Overgrazing on Soil Erosion and Land Degradation in a Dry Mediterranean Agro-Forest Landscape (Crete, Greece)

5sinoneThe impact of land management practices on soil erosion and land degradation was assessed during three consecutive years (December 2008–November 2011) in a rural area sensitive to desertification (Crete, Greece). The area is characterized by soils formed on flysch parent material, dry sub-humid climate with water deficit concentrated in summer, and frequent drought episodes. Precipitation, water runoff, sediment loss, soil moisture, air and soil temperature, and plant cover were recorded at two sites experiencing overgrazing and sustainable grazing. Sustainable grazing was associated with lower water runoff, reduced sediment loss and lower soil temperature than overgrazing. Plant cover protected soils from water erosion more effectively in the “sustainable grazing” plot than in the “overgrazing” plot. The study identifies overgrazing as a driver of land degradation in southern Europe and points out the contribution of sustainable management of pastoral landscapes in the mitigation of desertification risk.noneKairis O.; Karavitis C.; Salvati L.; Kounalaki A.; Kosmas K.Kairis, O.; Karavitis, C.; Salvati, L.; Kounalaki, A.; Kosmas, K