Monitoring 20 years of increased grazing impact on the Greek island of Crete with earth observation satellites

doi:10.1006/jare.1998.0392

Journal of Arid Environments

Volume 39, Issue 2, June 1998, Pages 165-178

https://doi.org/10.1006/jare.1998.0392 Get rights and content

Abstract

The degradation of permanent semi-natural vegetation and the resulting acceleration of soil degradation and erosion processes constitute major elements of land degradation in the Mediterranean basin. These elements are triggered by human activities rather than climatic conditions. The Greek island of Crete represents a characteristic case of land degradation resulting from hundreds of years of intensive grazing and fires. Since Greece joined the European Communities in 1981, grazing in mountainous regions has greatly increased due to subsidies that became available through the Common Agricultural Policy. Within a European Research Project on the use of satellite remote sensing for monitoring environmental change in Mediterranean ecosystems (DeMon-2:An Integrated Approach to Assess and Monitor Desertification Processes in the Mediterranean Basin), we have initiated a study to monitor the impact of increased grazing pressure on two mountainous ecosystems in Crete. The approach is based on describing surface conditions and vegetation cover over time with a long-term series of earth observation satellites.

References (27)

M.O. Smith et al.
Vegetation in deserts: I. a regional measure of abundance from multispectral images
Remote Sensing of Environment
(1990)
J.B. Adams et al.
Simple models for complex natural surfaces: a strategy for the hyperspectral era of remote sensing
Proceedings of the IGARSS ‘89 Symposium, July 10–14, Vancouver
(1989)
M. Arianoutsou-Faragitaki
Desertification by overgrazing in Greece. The case of Lesvos island
Journal of Arid Environments
(1985)
M.D. Craig
Minimum-volume transforms for remotely sensed data
Institute of Electrical and Electronics Engineers Transactions on Geoscience and Remote Sensing
(1994)
P. Gong et al.
Forest canopy closure from classification and spectral unmixing of scene components—multisensor evaluation of an open canopy
Institute of Electrical and Electronics Engineers Transactions on Geoscience and Remote Sensing
(1994)
R.D. Graetz
Remote sensing of terrestrial ecosystem structure: an ecologist's pragmatic view
Remote Sensing of Biosphere Functioning
(1990)
R.D. Graetz
Empirical and practical approaches to land surface characterisation and change detection
J. Hill
Monitoring land degradation and soil erosion in Mediterranean environments
ITC Journal
(1993)
J. Hill et al.
The Use of Remote Sensing for Land Degradation and Desertification Monitoring in the Mediterranean Basin. State of the Art and Future Research
(1996)
J. Hill et al.
Land degradation, soil erosion and desertification monitoring in Mediterranean ecosystems
Remote Sensing Reviews
(1995)

J. Hill et al.

Improved forest mapping by combining corrections of atmospheric and topographic effects

J. Hill et al.

Towards a satellite-observatory for mapping and monitoring the degradation of Mediterranean ecosystems

P. Hostert et al.

Employing a SPOT-derived orthophoto and DEM for geometrically correcting Landsat data

(1997)

Cited by (69)

Soil-sediment-configurations on slopes of Central and Western Crete (Greece) and their implications for late Holocene morphodynamics and pedogenesis – A conceptual approach
2022, Catena
Geomorphological processes and soil formation in slope positions within the Mediterranean area have been in the focus of research for a long time. Many of the surface-near soil-sediment-configurations in the Mediterranean area have been termed soils and have been interpreted as typical (zonal) Mediterranean reddish-brown soils (RMS) of Terra Rossa type associated with clay illuviation as main pedological process. However, there has been an extensive scientific debate which (late) Holocene geomorphological and pedological processes in fact dominate current soil-sediment-configurations, especially before the background of a long-lasting history of intense human land use impacts.
In the present study, we present field evidence as well as analytical data for a number of representative soil-sediment-profiles located in a variety of geological, geomorphological and climatic settings in central and western Crete (Greece). We have grouped the profiles in three schematic geomorphological categories in order to provide a geomorphological instead of a pedological context for their interpretation and comparison. Based on geochemical, mineralogical, geophysical and micromorphological evidence we could show that in most of the studied profiles, (late) Holocene pedogenesis is comparatively weak, except for bioturbation in combination with surprisingly high TOC-contents. Discontinuities within profiles are the result of geomorphological processes and the corresponding deposition of clearly distinguishable parent materials (substrates) rather than pedologic processes resulting in the in-situ differentiation of soil horizons. Furthermore, characteristic and ubiquitous peaks in grain size distribution within the clay and silt grain size fractions could be identified and are most likely related to long-range dust inputs. Whether the weak degree of recent pedogenesis is due to the long-lasting history of intense land use or rather due to the (naturally) high intensity of geomorphological processes and sediment relocation remains one of the main open questions raised by the results of this study.
Managing environmental challenges with anthropogenic bedrock modification: archaeological survey evidence from the Upper Basin (USA) and the island of Kos (Greece)
2021, Quaternary International
Citation Excerpt :
Today, vegetation varies across the elevational gradient, with the Dikaios upland maintaining forests of oak (Quercus spp.) and cypress (Cupressus spp.), while the alluvial plain is primarily agricultural (Fanouriou et al., 2018). In extensively grazed and deforested areas in the Dikaios uplands and on the more arid and grazed piedmont, phrygana vegetation communities dominate (see Arianoutsou, 1985; Diamantopoulos et al., 1994; Hill et al., 1998; Tsiourlis et al., 1998 for discussion of anthropogenic impacts to the development of phrygana communities). While dispersed perennial springs are known from antiquity and the ancient spring Bourina (Vourina) continues to supply water to modern Kos town (Sherwin White 1978, 16–17, notes 28–32, with previous bibliography), most springs are inactive today, likely due to increased runoff and decreased aquifer recharge resulting from modern deforestation (Higgins and Higgins, 1996, 161) and agriculture.
Human-environmental interaction studies typically focus on large-scale landscape modifications of vegetation or soils and rarely address smaller-scale human alterations to site settings. This approach is based on a broad concept of environment as “set” having spatially dispersed and regionally defined attributes, as opposed to something that is mutable at the scale of individual groups of humans living at a specific location. This paper examines how two prehistoric groups, the Final Neolithic to Early Bronze Age 2 occupants on the island of Kos, Greece and the Late Formative Period occupants in the Upper Basin, northern Arizona, selected and modified habitation locations involving exposed bedrock. Although chronologically separated by thousands of years and occupying different continents, these two groups share similarities in population size, socio-political complexity, and environmental challenges. In facing these challenges, both groups apply practical, but different, approaches that utilized one of the most prevalent globally available resources -- limestone bedrock.
Free behind bars: Effects of browsing exclusion on the growth and regeneration of Zelkova abelicea
2021, Forest Ecology and Management
Citation Excerpt :
During the 20th century, due to the socioeconomic changes that shook Europe after the Second World War, pastoralism drastically changed on Crete. Although the number of farms decreased, more intensive practices arose, and the number of sheep and goats increased almost exponentially, even more so after the adhesion of Greece to the European Union in 1981 and the access to subsidies delivered to farmers per animal (Bauer and Bergmeier, 2011, Hill et al., 1998, Hostert et al., 2003, Ispikoudis et al., 1993, Kizos et al., 2014, Kosmas et al., 2016, Lyrintzis, 1996, Lorent et al., 2009). At the same time, there has been a strong development of roads in the mountains, also supported by European Union subsidies, making remote areas easier to access and to bring bigger flocks (Hill et al., 1998, Hostert et al., 2003).
Caprine overbrowsing is a main threat to trees of pastoral mountain woodlands in the Mediterranean region of Europe. In this study, we assess the impact of browsing exclusion on the growth and regeneration of the endangered Zelkova abelicea, a Paleogene relict tree endemic to Crete (Greece). Shoot elongation, height growth and natural regeneration were monitored during two to five years in 31 fenced plots across the distribution range of the species. We found that in the absence of browsing pressure, Z. abelicea produces shoots on average two times longer than when browsed, therefore clearly demonstrating the negative impact of current browsing pressure on the growth performance of the species. Shoot elongation and height growth were maximal in most plots during the first two years following fencing, after which growth rates decreased. The proportion of trees that reached a height considered out of reach of caprine browsing had more than doubled already after four years, although this was dependent on initial tree height. Shoot elongation and height growth were positively correlated with tree height, and smaller trees took more time to reach a specific height. Seedlings were only found in three fenced plots as well as in two control browsed areas during a single year and only in western Crete. This underlines the possible strong and concerning impact of climatic factors on seed formation as well as on seedling growth and survival, although site specificities such as stand structure and micro-topography should also be considered. Our findings have important implications for conservation actions, as they can help choose which stands and which individuals to fence in priority for efficient long-term conservation.
Modification and validation of the SWAT model based on multi-plant growth mode, a case study of the Meijiang River Basin, China
2020, Journal of Hydrology
Citation Excerpt :
In our study, based on a linear mixed model, the spatial distribution of dominant vegetation abundance in the study area was obtained using remote sensing. The linear mixed model assumed the spectra of mixed pixels to be a linear combination of the spectra of the various surface features within the instantaneous field of view (Adams et al., 1986; Hilll et al., 1998). According to actual ground cover in the study area, the ground cover of the area was divided into seven components: broadleaf forest, coniferous forest, grassland and sparse shrubs, bare land, water body, cultivated land, and residential land.
With the aim of simulating non-point source pollution of the agroforestry system, we established a forest growth model featuring variable density and mixed vegetation types to address the drawbacks of the Soil and Water Assessment Tool (SWAT) in estimating the accumulated biomass, based on the average forest vegetation density and single plant growth pattern. In addition, a dominant vegetation abundance remote sensing inversion model and leaf area index (LAI) and extinction coefficient remote sensing inversion model were set up to obtain relevant parameters of the forest growth model. Moreover, based on radiant energy under intercropping, we used the Keating equation with the intercropping index as the variable to modify the original SWAT single biomass accumulation model. This was done to explore the intercropping growth model as well as the remote sensing inversion method, considering the multiple cropping and intercropping indexes. We selected the Meijiang River basin as the study area, a sub-basin of the Poyang Lake basin in China in a subtropical humid monsoon climate zone and red soil region, to explore the validity of the modified SWAT based on field data. The results show that the modified SWAT outperformed the original model in terms of simulated flow and nutrient load, using variables such as vegetation coverage, different forest components (e.g., coniferous forest, broadleaf forest, and sparse shrubs), and LAI. As for simulated flow, the validity of the modified SWAT was increased by 7.8%, and simulation of the average, maximum, minimum, and total flow rates were closer to the measured values, better reflecting the actual surface water storage. In the simulation of nutrient load, validity was increased by 6.4% (total phosphorus) and 6.1% (total nitrogen), better representing macroscopic and microscopic characteristics of the forest vegetation landscape.
A race to the unknown: Contemporary research on tree and forest drought resistance, an Israeli perspective
2020, Journal of Arid Environments
Forestry at the dry edge of forest existence has been a long-lasting interest to arid land residents. Current land-use and climate changes have broaden this interest to the global society, seeking for improved tree and forest drought resistance across biomes. Within this transition, Israel is a hub for scientific research and testing ground alike. Israel is a small country, spanning over arid, semi-arid, and thermo-Mediterranean environments, with relatively little forest. Nevertheless afforestation efforts have been unprecedented (by percent change in land cover), and many of these forests serve today as a ‘living lab’ for forest and tree drought resistance research. Considering the ongoing warming and drying, tree physiologists, forest ecologists, and forest managers in Israel are running a race to the unknown. To ensure local forest sustainability for future generations, the gap between the increased drought risk on the one hand, and the rather stationary forest drought resistance on the other hand, must be closed. The aim of this review is to highlight the findings and achievements, as well as challenges, of this contemporary research. Examples from Israel are given at the Middle East, and the wider, global arid land, contexts. In particular, important progress has been made in the following aspects: (1) the physiology of tree drought resistance, including water-use traits and phenology; (2) the genetic approach, advancing from provenance trials, to the application of molecular tools in the identification of tree drought resistance mechanisms; (3) the canopy flux measurement approach, e.g. monitoring the exchange of carbon, water, and energy in water-limited forests; (4) the application of remote sensing tools, such as satellite-based vegetation indices; and (5) the application of adaptive management practices in increasing forest resilience under drought. Taken together, these advances represent a way forward, while indicating important gaps, and open questions to future research. Lessons learnt in forests in Israel should be useful and transferable to other forest ecosystems in the Middle East, the Mediterranean, and additional water-limited regions.
Overgrazed shrublands support high taxonomic, functional and temporal diversity of Mediterranean ground spider assemblages
2019, Ecological Indicators
Citation Excerpt :
In the Mediterranean region, overgrazing has been pernicious, causing a shift in the soil nutrient status which may result in decreased primary production and matches degradation, especially in cases of large increases in livestock numbers (Perevolotsky and Seligman, 1998). Several locations in Crete, the largest island in Greece and fifth largest in the Mediterranean, represent characteristic cases of human induced land degradation, as well as decreasing vegetation cover and richness due to uninterrupted intensive grazing (Hill et al., 1998). Livestock grazing is an old, historically consistent human activity and an essential part of the ecosystems of Crete (Vogiatzakis and Rackham, 2008).
The phryganic and maquis shrublands form the most typical vegetal formations in the Eastern Mediterranean that since thousands of years have been subject to various types of anthropogenic disturbance, including grazing. We studied the impact of sheep and goat grazing on 50 assemblages of ground spiders (Araneae: Gnaphosidae) in phryganic, maquis and forest habitats from zero to 2000 m elevation on Crete, Greece using pitfall traps for one year at each sampling site. In total, 58 gnaphosid species and 16,592 individuals were collected. Cretan endemic Gnaphosidae were negatively affected by intensive grazing and, contrary to findings on other taxa studied on the island, they were sparse and rare throughout the study area. The species composition of gnaphosid assemblages was primarily determined by elevation. Trachyzelotes lyonneti, Urozelotes rusticus, Zelotes scrutatus, Anagraphis pallens and Berinda amabilis proved to be significant indicators of overgrazing. The vast majority of spiders belonging to synanthropic and nationally red-listed species were found in overgrazed sites. Despite theoretical expectations, while the average activity density decreased, the number of species, evenness, rarity, taxonomic, temporal and functional diversity (FRic) indices increased with increasing grazing intensity. This was mainly due to the nature of disturbance itself, which probably allows equibalanced low abundances of indigenous or synanthropic species, rather than overdominance of few, thus partly refuting the opportunistic species hypothesis (OSH). Ground spider assemblages in overgrazed sites comprised sparse populations of mostly rare, opportunistic species with different combinations of life-history traits that partly replace other species more commonly found in the less degraded sites. Species of these assemblages shorten their phenologies to minimize temporal co-occurrence with each other due to resource limitation. These distinct community patterns highlight ground spiders as good indicators of grazing pressure on Crete, on species and assemblage level. To conserve the indigenous and potentially endangered invertebrate fauna, the spatiotemporal discontinuity of grazing including rested patches is important in order to maintain spatial variability and possibly lead to habitat restoration.

View all citing articles on Scopus

^☆: Hobbs, R. J.&Mooney, H. A.

View full text

Regular ArticleMonitoring 20 years of increased grazing impact on the Greek island of Crete with earth observation satellites☆

Abstract

Remote Sensing of Environment

Simple models for complex natural surfaces: a strategy for the hyperspectral era of remote sensing

Proceedings of the IGARSS ‘89 Symposium, July 10–14, Vancouver

Desertification by overgrazing in Greece. The case of Lesvos island

Journal of Arid Environments

Minimum-volume transforms for remotely sensed data

Institute of Electrical and Electronics Engineers Transactions on Geoscience and Remote Sensing

Forest canopy closure from classification and spectral unmixing of scene components—multisensor evaluation of an open canopy

Institute of Electrical and Electronics Engineers Transactions on Geoscience and Remote Sensing

Remote sensing of terrestrial ecosystem structure: an ecologist's pragmatic view

Remote Sensing of Biosphere Functioning

Empirical and practical approaches to land surface characterisation and change detection

Monitoring land degradation and soil erosion in Mediterranean environments

ITC Journal

The Use of Remote Sensing for Land Degradation and Desertification Monitoring in the Mediterranean Basin. State of the Art and Future Research

Land degradation, soil erosion and desertification monitoring in Mediterranean ecosystems

Remote Sensing Reviews

Improved forest mapping by combining corrections of atmospheric and topographic effects

Towards a satellite-observatory for mapping and monitoring the degradation of Mediterranean ecosystems

Employing a SPOT-derived orthophoto and DEM for geometrically correcting Landsat data

Regular Article
Monitoring 20 years of increased grazing impact on the Greek island of Crete with earth observation satellites☆