Abstract

The objective of this work was to classify and map the areas environmentally sensitive to desertification in the Mediterranean island of Crete. Sensitivity to desertification was estimated with a modification of the MEDALUS Environmentally Sensitive Area Index (ESAI) approach, using 15 quantitative parameters divided into four main quality indices: climate, vegetation, soils and management quality. The ESAI methodology was modified to include two additional parameters related to soil quality (water erosion and soil organic matter). According to the results, 37% of the island's area is characterized as critically sensitive to desertification. This percentage varies significantly across the island, with the western part having the least critically sensitive areas, and the eastern part the most critically sensitive. The results of this study also indicate that critically sensitive areas are found in the eastern side of the island mainly due to human-related factors and climatic conditions. It was concluded that the proposed methodology is a valuable tool for regional-scale assessment of areas environmentally sensitive to desertification in Mediterranean environments.

INTRODUCTION

Desertification is one of the major hazards threatening arid and semi-arid regions, and is regarded as one of the most important global environmental problems of the 21st century. Therefore, mapping the areas sensitive to desertification has become a crucial task in order to mitigate potential effects of anthropogenic and environmental impacts. Various definitions of desertification have been given over recent decades by several authors (Mainguet 1991; UNEP 1992; Lambin et al. 2001; Geist & Lambin 2004; Reynolds et al. 2007; Reed & Stringer 2016). The most widely known definition has been given by the United Nations Convention to Combat Desertification (UNCCD). According to this, desertification is the ‘land degradation that occurs mainly in arid, semi-arid and dry sub-humid areas’ and land degradation is the ‘reduction or loss in the biological or economic productive capacity of the land caused by human activities and often magnified by the impacts of climate change’ (UNCCD 1994).

The risk of desertification in combination with the expected changes in climate is a significant threat in several regions of the Mediterranean area. Desertification is a process that can affect the ecosystem of an area, and it can also affect the quantity and quality of water resources and reduce agricultural productivity. According to the UNCCD (2004), the countries of the Mediterranean region have a recognized desertification problem and are characterized as vulnerable to climate change (Drake & Vafeidis 2004; Kepner et al. 2006; Sommer et al. 2011; Symeonakis et al. 2016).

Land degradation happens due to a number of reasons. Mainly, the desertification that is occurring around the world today is caused by human activity on lands that are extremely vulnerable to overexploitation and improper agricultural methods. Overgrazing and deforestation are two of the main causes of desertification. Especially, in arid regions, grass, trees and other vegetation are necessary to prevent soil erosion and nutrient loss. In addition, improper agricultural practices such as long-term conventional tillage may also lead to land being more vulnerable to desertification.

Various models and methodologies have been proposed to assess desertification (Babaev 1985; Oldeman et al. 1991; Kosmas et al. 1999; Brandt et al. 2003; DESERTLINKS 2004). The Environmental Sensitivity Area Index (ESAI) approach (Kosmas et al. 1999) is the procedure most used to estimate degradation risk in the Mediterranean region. The Environmental Sensitivity Area (ESA) output is an indicator system producing a warning index (ESAI) constituted by more than 10 variables assessing environmental quality (i.e. soil, vegetation, climate), as well as anthropogenic factors (land management) (Basso et al. 2000). The ESA methodology was applied to case studies in Italy (Basso et al. 2000; Coscarelli et al. 2005; Salvati & Zitti 2009; Ladisa et al. 2012; Salvati et al. 2015), the Spanish Province of Extremadura (Lavado Contador et al. 2009), southern Iran (Sepehr et al. 2007), Egypt (Bakr et al. 2012) and Algeria (Boudjemline & Semar 2018). In Greece, a continuous monitoring system of environmental sensitivity to land degradation of the island of Lesvos has been investigated through the ESA approach (Kosmas et al. 1999; Symeonakis et al. 2016).

The main purpose of this work was to recognize and map areas environmentally sensitive to desertification on a typical Mediterranean island (Crete) in the frame of the LIFE+ AGROCLIMAWATER project, which aims to prepare the agricultural sector to adapt to climate change. The Greek National Committee for Combating Desertification considers Crete to be a high-risk area for desertification because of deforestation of sloping lands, intensive cultivation and overgrazing, in combination with high spatio-temporal variation of climatic factors (Croke et al. 2000; Panagos et al. 2014).

Taking into consideration that the island of Crete has been characterized as one of the major drought-prone areas in the Mediterranean zone (Kourgialas et al. 2018), one of the aims of this study was the development, for the first time, of a desertification-prone areas map for the island of Crete. Thus, this study employed a modification of the MEDALUS approach by adding, for the first time, two extra parameters in terms of soil quality: water erosion and soil organic matter. This study highlights the combined role of these two parameters in defining the desertification risk areas in Mediterranean environments. Up to now, in assessing desertification, soil erosion and soil organic matter parameters have been used separately by Symeonakis et al. (2016) and Sepehr et al. (2007), respectively. Organic matter affects both the chemical and physical properties of the soil (soil structure; moisture holding capacity; diversity and activity of soil organisms, and nutrient availability). It also influences the effects of chemical amendments, fertilizers, pesticides and herbicides. Organic materials that cover the soil surface protect the soil from sealing and crusting by raindrop impact, thereby enhancing rainwater infiltration and reducing runoff (Bot & Benites 2005). On the other hand, soil erosion, especially in arid and semi-arid lands, contributes to soil degradation, which in turn affects the sustainable agricultural land use and productivity (Kourgialas et al. 2016).

MATERIALS AND METHODS

Study area

Crete is an island of southern Greece, located in the Mediterranean Sea (35:20:27 N, 25:07:46 E) (Figure 1). It covers an area of approximately 8,264 km2. It is mostly mountainous, with a mean elevation of 482 m and a highest peak of approximately 2,400 m (Psiloritis Mountain). The mountainous terrain is often interrupted by lowlands, which sometimes extend to the sea. The western part of Crete includes Chania and Rethymno prefectures, and the eastern part includes the prefectures of Herakleio and Lasithi (Figure 1). The agricultural area of the island is about 3,205 km2. In addition, the major water use in Crete is for irrigation purposes (84.5% of total consumption), while domestic and industrial use is about 15.5%.

Figure 1

The island of Crete. Upper panel: location of Crete (black frame). Lower panel: elevation map of Crete with the locations of the four largest cities as well as the main agricultural regions of the island (red ellipses). Weather stations are marked by blue squares. The full colour version of this figure is available in the online version of this paper, at http://dx.doi.org/10.2166/wcc.2018.148.

Figure 1

The island of Crete. Upper panel: location of Crete (black frame). Lower panel: elevation map of Crete with the locations of the four largest cities as well as the main agricultural regions of the island (red ellipses). Weather stations are marked by blue squares. The full colour version of this figure is available in the online version of this paper, at http://dx.doi.org/10.2166/wcc.2018.148.

The eight main intensive agricultural regions are dominated by tree crops (olive, citrus, avocado), vineyards, and greenhouse vegetation cultivation, and are presented with red ellipses in Figure 1. The agricultural areas in the western part of the island are characterized by coarse and medium soil texture and are considered as areas where olive, avocado and citrus trees thrive due to the local climate conditions. On the other hand, the agricultural areas in the eastern part of the island are characterized by fine soil texture and drier climate conditions. The dominant crops in this part of the island are olive trees and grape vines. Among these crops, olive can be considered as remarkably drought-tolerant (Koubouris et al. 2015).

The climate is typical of the Mediterranean region, with humid and relatively cold winters and dry and warm summers. The average annual precipitation is about 665 mm, of which over 95% occurs between October and May (Kourgialas & Karatzas 2016). Significant rainfall differences are recorded between the western and eastern areas of the island during the wet seasons. According to Panagos et al. (2014) and the European Soil Database, soils in Crete are generally poorly developed and shallow. Limestone and dolomites dominate the mountain terrain, whereas Neogene sediments, including limestones, sandstones and marls, cover large areas of the lowlands (Sarris et al. 2005). According to the Institute of Geology & Mineral Exploration (Greece), there are also phyllites (fine-grained metamorphic rocks), flyschs (sequences of sedimentary rock layers), pyroclastic rocks and alluvial deposits on the island. In terms of vegetation, Crete is mostly covered by natural grasslands and pastures. Olive groves are the most extensive croplands and, with vineyards, fruit plantations and few other agricultural areas, occupy a significant part of the land. Evergreen forests, coniferous forests and Mediterranean maquis cover less than 5% of the island (CLC 2012).

ESAI methodology

The environmental sensitivity of an area is related to several environmental and socio-economic factors. ESA is closely related to many environmental factors such as climate, soil, vegetation cover and morphology where their characteristics, and their intensity, contribute to the evolution and characterization of different degradation levels or stages (Basso et al. 2000).

In this study, the criteria defined by Basso et al. (2000) were used to select the different layers of parameters for mapping sensitive areas according to the MEDALUS–ESAI methodology (Kosmas et al. 1999) in combination with the availability of data for the study area. Fifteen layers belonging to four main environmental quality indices related to climate, vegetation, soil and land management of the area were estimated and their values standardized between 1 (low sensitivity) and 2 (high sensitivity) (Tables 14). The four quality indices were estimated using Equation (1) (see also Figure 2 for a flowchart of the methodological framework): 
formula
(1)
where: Qualityx represents the computed value of each quality and n represents the number of sub-indicators (layers) used to calculate each quality index. In the last ESAI stage, the final sensitivity of an area is evaluated from the four quality indices, obtained from the above equation, in a linear way: 
formula
(2)
Table 1

Main indicators of adopted classification scheme: scores and methods used in the GIS to estimate the climate quality index

 Parameter Classes Index Data/source 
Climate quality Rainfall (mm) >650 Data from meteorological stations of the island 
280–650 1.5 
<280 
Aridity = Precipitation/PET >0.65 PET: FAO − 56 Penman–Monteith equation (Allen et al. 1998), mean monthly min and max temperature from the meteorological stations of the island 
0.5–0.65 1.5 
<0.5 
Aspect N, NE, NW 20 m–pixel DEM
Hellenic Military Geographical Service 
S, SE, SW 
 Parameter Classes Index Data/source 
Climate quality Rainfall (mm) >650 Data from meteorological stations of the island 
280–650 1.5 
<280 
Aridity = Precipitation/PET >0.65 PET: FAO − 56 Penman–Monteith equation (Allen et al. 1998), mean monthly min and max temperature from the meteorological stations of the island 
0.5–0.65 1.5 
<0.5 
Aspect N, NE, NW 20 m–pixel DEM
Hellenic Military Geographical Service 
S, SE, SW 
Table 2

Main indicators of adopted classification scheme: scores and methods used in the GIS to estimate the vegetation quality index

 Parameter Classes Index Data/source 
Vegetation quality Drought resistance Evergreen forests (except coniferous), mixed Mediterranean maquis-evergreen forests Corine Land Cover (CLC) for the year 2012. Source: http://www.data.gov.gr/dataset/xartes-kalypshs-ghs-corine-land-cover-gia-ta-eth-2006-and-2012 
Conifer forests, deciduous forests and olives 1.2 
Almonds, orchards and vines 1.4 
Perennial grasslands, pastures and shrubland 1.7 
Annual crops (annual grassland, cereals, maize and sunflower), horticulture and very low vegetated 
Erosion protection Evergreen forest (except conifers), mixed Mediterranean maquis-evergreen forest 
Mediterranean maquis, conifer forests, perennial grasslands, pastures, olives and shrubs 1.3 
Deciduous forests (oak and mixed) 1.6 
Almonds and orchards 1.8 
Vines, horticulture, annual crops, very low vegetated and bare soils 
Fire risk Almonds, orchards, vines, olives, irrigated annual crops and horticulture 
Perennial grasslands, pastures, cereals, annual grasslands, deciduous forests (oak and mixed), mixed Mediterranean maquis, evergreen forests, very low vegetated and shrublands 1.3 
Mediterranean maquis 1.6 
Pines and other conifer forests 
Plant cover (%) >40 
10–40 1.8 
<10 
 Parameter Classes Index Data/source 
Vegetation quality Drought resistance Evergreen forests (except coniferous), mixed Mediterranean maquis-evergreen forests Corine Land Cover (CLC) for the year 2012. Source: http://www.data.gov.gr/dataset/xartes-kalypshs-ghs-corine-land-cover-gia-ta-eth-2006-and-2012 
Conifer forests, deciduous forests and olives 1.2 
Almonds, orchards and vines 1.4 
Perennial grasslands, pastures and shrubland 1.7 
Annual crops (annual grassland, cereals, maize and sunflower), horticulture and very low vegetated 
Erosion protection Evergreen forest (except conifers), mixed Mediterranean maquis-evergreen forest 
Mediterranean maquis, conifer forests, perennial grasslands, pastures, olives and shrubs 1.3 
Deciduous forests (oak and mixed) 1.6 
Almonds and orchards 1.8 
Vines, horticulture, annual crops, very low vegetated and bare soils 
Fire risk Almonds, orchards, vines, olives, irrigated annual crops and horticulture 
Perennial grasslands, pastures, cereals, annual grasslands, deciduous forests (oak and mixed), mixed Mediterranean maquis, evergreen forests, very low vegetated and shrublands 1.3 
Mediterranean maquis 1.6 
Pines and other conifer forests 
Plant cover (%) >40 
10–40 1.8 
<10 
Table 3

Main indicators of adopted classification scheme: scores and methods used in the GIS to estimate the soil quality index

 Parameter Classes Index Data/source 
Soil quality Parent material Shale, schist, basic, ultra-basic, conglomerates, unconsolidated, clays and marl (with natural vegetation) Geological maps were bought from the Institute of Geology & Mineral Exploration 
Limestone, marble, granite, rhyolite, ignibrite, gneiss, siltstone, sandstone and dolomite 1.7 
Marl and pyroclastics 
Texture LSCL, SL, LS and CL The map produced by the Institute of Geology and Mineral Exploration was downloaded from the European Soil Data Centre (ESDAC). https://esdac.jrc.ec.europa.eu/content/topsoil-physical-properties-europe-based-lucas-topsoil 
SC, SiL and SiCL 1.2 
Si, C and SiC 1.6 
Soil depth (cm) >75 
30–75 1.3 
15–30 1.6 
<15 
Soil organic matter (%) <0.5 The map was downloaded from: https://esdac.jrc.ec.europa.eu/content/octop-topsoil-organic-carbon-content-europe 
0.5–1 1.7 
1–2 1.5 
2–3 1.2 
>3 
Water erosion (tn/ha/yr) <1 A map was produced by Panagos et al. (2014) 
https://esdac.jrc.ec.europa.eu/content/g2-soil-erosion-model-data-crete-greece-and-strymonas-greecebulgaria-ishmi-erzeni-albania 
1–5 1.3 
5–20 1.7 
>2 
Slope gradient <6 20 × 20 m–pixel DEM Hellenic Military Geographical Service 
6–18 1.2 
18–35 1.5 
>35 
 Parameter Classes Index Data/source 
Soil quality Parent material Shale, schist, basic, ultra-basic, conglomerates, unconsolidated, clays and marl (with natural vegetation) Geological maps were bought from the Institute of Geology & Mineral Exploration 
Limestone, marble, granite, rhyolite, ignibrite, gneiss, siltstone, sandstone and dolomite 1.7 
Marl and pyroclastics 
Texture LSCL, SL, LS and CL The map produced by the Institute of Geology and Mineral Exploration was downloaded from the European Soil Data Centre (ESDAC). https://esdac.jrc.ec.europa.eu/content/topsoil-physical-properties-europe-based-lucas-topsoil 
SC, SiL and SiCL 1.2 
Si, C and SiC 1.6 
Soil depth (cm) >75 
30–75 1.3 
15–30 1.6 
<15 
Soil organic matter (%) <0.5 The map was downloaded from: https://esdac.jrc.ec.europa.eu/content/octop-topsoil-organic-carbon-content-europe 
0.5–1 1.7 
1–2 1.5 
2–3 1.2 
>3 
Water erosion (tn/ha/yr) <1 A map was produced by Panagos et al. (2014) 
https://esdac.jrc.ec.europa.eu/content/g2-soil-erosion-model-data-crete-greece-and-strymonas-greecebulgaria-ishmi-erzeni-albania 
1–5 1.3 
5–20 1.7 
>2 
Slope gradient <6 20 × 20 m–pixel DEM Hellenic Military Geographical Service 
6–18 1.2 
18–35 1.5 
>35 
Table 4

Main indicators adopted classification scheme – scores and methods used in the GIS to estimate the management quality index

 Parameter Classes Index Data/source 
Management quality Intensity of land use Woodlands, semi-natural areas and natural grasslands Corine Land Cover (CLC) for the year 2012 (CLC 2012)  
Irrigated and non-irrigated vineyards, irrigated and non-irrigated fruit trees, irrigated and non-irrigated olive groves, annual crops associated with permanent crops, complex cultivation patterns, land principally occupied by agriculture with significant areas of natural vegetation, non-irrigated arable land 1.5 
Open field herbaceous with spring–summer cycle, horticulture with spring–summer cycle, greenhouses 
Protection policies Reserves, parks and archaeological areas Sites of Community Importance (SCI) and Special Protected Areas (SPA) according to the EU Directive 92/43. Source: http://www.ypeka.gr/?tabid=504 
Woodlands, semi-natural and coastal areas 1.5 
Areas not subject to restrictions 
 Parameter Classes Index Data/source 
Management quality Intensity of land use Woodlands, semi-natural areas and natural grasslands Corine Land Cover (CLC) for the year 2012 (CLC 2012)  
Irrigated and non-irrigated vineyards, irrigated and non-irrigated fruit trees, irrigated and non-irrigated olive groves, annual crops associated with permanent crops, complex cultivation patterns, land principally occupied by agriculture with significant areas of natural vegetation, non-irrigated arable land 1.5 
Open field herbaceous with spring–summer cycle, horticulture with spring–summer cycle, greenhouses 
Protection policies Reserves, parks and archaeological areas Sites of Community Importance (SCI) and Special Protected Areas (SPA) according to the EU Directive 92/43. Source: http://www.ypeka.gr/?tabid=504 
Woodlands, semi-natural and coastal areas 1.5 
Areas not subject to restrictions 
Figure 2

Flowchart of the methodological framework for the estimation of the Environmentally Sensitive Area Index.

Figure 2

Flowchart of the methodological framework for the estimation of the Environmentally Sensitive Area Index.

The ESAI gives equal weights to each layer when computing each quality (e.g. soil texture has the same weight as soil erosion), as well as equal weights to each Qualityx, when computing the overall environmental sensitivity index. This means that a Qualityx is not considered of less importance if fewer layers are used for its computations (Symeonakis et al. 2016).

The data shown in Figure 2 are required for the definition of areas environmentally sensitive to desertification: (a) soil data, (b) vegetation data, (c) climate data, and (d) land management characteristics. Information on soil, geology, climate, vegetation cover, erosion and other factors was collected from various sources (Tables 14).

Climate quality was calculated from indicators, such as the amount of precipitation, that influence availability of water to plants. Annual precipitation was classified in three classes, considering that annual precipitation of 300 mm is a critical threshold for plant growth (Sepehr et al. 2007). The simple FAO aridity index was also used in this study (Allen et al. 1998). The aridity index is the ratio of the annual precipitation divided by the annual potential evapotranspiration (P/PET). Precipitation and evapotranspiration data were collected from several meteorological stations distributed all over the island providing enough coverage (Figure 1). Aspect was derived from a digital elevation model at 20-m resolution scale.

Soil data were obtained from the European Soil Database (ESDCAC) and the Hellenic Institute of Geology & Mineral Exploration (IGME). Considering the aim of the study, the soil variables used are texture, slope, parent material, soil depth, organic matter and soil erosion. Data on soil erosion caused by water were obtained from the study of seasonal and annual erosion assessments in Mediterranean agricultural areas using the G2 model (Panagos et al. 2014).

The vegetation and land management quality maps were produced according to the Corine Land Cover of the year 2012 in accordance with the deliverables of the CORINE programme of the European Union (CLC 2012). Finally, the protection policies data were derived from Sites of Community Importance (SCI) and Special Protected Areas (SPA) according to the EU Directive 92/43 (NATURA 2000).

RESULTS AND DISCUSSION

The resulting maps for the four quality indices are shown in Figure 3. For reasons of simplicity, the quantitative results are classified into three qualitative classes (low, moderate and high sensitivity to desertification) according to the scheme suggested by Sepehr et al. (2007; Table 5).

Figure 3

Sensitivity maps of: (a) climate sensitivity index; (b) vegetation sensitivity index; (c) soil sensitivity index; and (d) management sensitivity index.

Figure 3

Sensitivity maps of: (a) climate sensitivity index; (b) vegetation sensitivity index; (c) soil sensitivity index; and (d) management sensitivity index.

Table 5

Sensitivity classes of the four quality indices, according to the classification suggested by Sepehr et al. (2007) 

Quality index Range Sensitivity class 
Climate quality index Low 
1.1–1.5 Moderate 
1.5–2 High 
Vegetation quality index <1.13 Low 
1.13–1.38 Moderate 
>1.38 High 
Soil quality index <1.13 Low 
1.13–1.45 Moderate 
>1.45 High 
Management quality index 1–1.3 Low 
1.3–1.5 Moderate 
>1.5 High 
Quality index Range Sensitivity class 
Climate quality index Low 
1.1–1.5 Moderate 
1.5–2 High 
Vegetation quality index <1.13 Low 
1.13–1.38 Moderate 
>1.38 High 
Soil quality index <1.13 Low 
1.13–1.45 Moderate 
>1.45 High 
Management quality index 1–1.3 Low 
1.3–1.5 Moderate 
>1.5 High 

In terms of climate sensitivity (Figure 3(a)), the western part of the island was mapped as having high–moderate climatic quality and the eastern as low quality. This could be attributed to the fact that eastern areas (south Herakleio and Lasithi prefecture) receive less precipitation than the western part of the island.

Regarding the vegetation sensitivity index, areas with low drought resistance (e.g. agricultural areas), with high fire risk (e.g. pine forests) and with low percentage of vegetation cover are identified as highly sensitive in terms of their vegetation quality. As Figure 3(b) shows, the greater part of the island is characterized by moderate vegetation sensitivity except for some parts of Herakleio prefecture, which are characterized by high vegetation sensitivity due to anthropogenic processes and the drier climate conditions. Considering also that vegetation cover is a crucial element in soil erosion control on sloping areas, a considerable part of the island's natural lands are subject to very high erosion risk due to animal breeding activities (overgrazing).

Figure 3(c) shows the resulting soil quality map of the island. The areas with the most sensitive soils are found at the southwest part of the island, in the major part of Herakleio prefecture and in the eastern part of Lasithi prefecture. The rest of the island has moderate soil sensitivity. This results from the presence of large areas with slopes greater than 18%, frequent presence of soils less than 30 cm deep and an important presence of clay soils. The results of soil quality are also related to the high rates of soil erosion and the poor soil organic content.

In terms of the management policies dimension, Figure 3(d) shows that the northern part of Chania prefecture and the major part of Herakleio prefecture are considered very sensitive regarding land management. During recent decades, the intensity of grazing has increased dramatically and a large share of vineyards was replaced by olive and fruit orchards (Karydas et al. 2008). The southern areas of Chania prefecture and certain areas in the eastern part of the island are covered by pine or oak forests and are considered well managed and environmentally protected (low sensitivity). Large parts of these areas are also managed by environmental protection policies (e.g. NATURA (2000) areas and Important Bird Areas).

Crete's environmental sensitivity to desertification, according to the ESA approach, is shown in Figure 4(a). According to these results and Table 6, the vast majority of the island is considered as fragile or critical for desertification. The most sensitive parts (critical areas) are found mainly in the southern and eastern part of Crete. These areas have badly degraded, very shallow (depth 0–15 cm) to shallow (15–30 cm) soils and are poorly vegetated. They are also very sensitive to low rainfall events and high temperatures. The fragile areas (F1, F2 and F3) are more widespread along the island and are represented by zones in which management factors, quality of soil and climate are not very critical. Due to the relatively good vegetation cover, the soils of this zone are moderately shallow (depth 30–50 cm) to moderately deep (50–100 cm). The Potential environmentally sensitive and the Not affected areas are mainly located in the western and middle parts of the island where favourable climate (high annual rainfall) and efficient land management are found. Out of the total area of Crete (8,264 km2), 3,050 km2 are characterized as areas critically sensitive to desertification (C1, C2 and C3), corresponding to the 37% of the total area. In addition, extended areas from seven of the total eight main agricultural regions of Crete are characterized as critically sensitive to desertification. Therefore, only one intensive agricultural region in Crete (the Prefecture of Rethymno) seems to not be prone to desertification risk as the desertification ranges from not affected to fragile (Figure 4(b)).

Figure 4

(a) Map of environmentally sensitive areas on Crete related to desertification risk. (b) Critically sensitive areas for desertification on Crete and the eight main agricultural regions.

Figure 4

(a) Map of environmentally sensitive areas on Crete related to desertification risk. (b) Critically sensitive areas for desertification on Crete and the eight main agricultural regions.

Table 6

Classes of ESAI and the corresponding ranges of indices

ESAI index ESAI classification 
<1.17 Not affected 
1.17–1.22 Potential 
1.23–1.26 Fragile (F1) 
1.26–1.32 Fragile (F2) 
1.33–1.37 Fragile (F3) 
1.38–1.41 Critical (C1) 
1.42–1.53 Critical (C2) 
>1.53 Critical (C3) 
ESAI index ESAI classification 
<1.17 Not affected 
1.17–1.22 Potential 
1.23–1.26 Fragile (F1) 
1.26–1.32 Fragile (F2) 
1.33–1.37 Fragile (F3) 
1.38–1.41 Critical (C1) 
1.42–1.53 Critical (C2) 
>1.53 Critical (C3) 

The MEDALUS approach is one of the most widely used empirically based models for predicting and mapping desertification. In the present study a modification of the MEDALUS approach, amended by adding, for the first time, two extra parameters in terms of soil quality – water erosion and soil organic matter – was applied in the geographic information system (GIS) environment. The proposed methodology presents an improvement over the common MEDALUS approach, since it incorporates all the information necessary to reduce the level of uncertainty in the results.

In Mediterranean environments, as elsewhere, desertification can cause irreversible damage to local and regional production structures, particularly in areas that are heavily reliant on agricultural activity. In such instances, local authorities are forced to deal with the negative socio-economic effects associated with rising unemployment and declining incomes. The results of this study should alert local authorities considering measures to prevent or/and mitigate desertification. Specifically, the proposed ESAI maps could become a valuable tool for the local authorities in order to inform farmers about the measures to be taken for the mitigation of the effects. Farmers could be informed by local authorities and researchers as to whether their properties are in a critical desertification risk region, as well as of the preventive measures that should be applied in such cases.

CONCLUSIONS

In this study, sensitivity to the desertification process occurring in a typical Mediterranean island (Crete) was investigated using a modification of the MEDALUS methodology. The flexibility of the MEDALUS–ESAI methodology in relation to the data availability enabled us to provide a final map of sensitivity to desertification for the Mediterranean island. The proposed methodology presents an improvement over the common MEDALUS approach, since it incorporates all information necessary to reduce the level of uncertainty in the results. An important part of the island is characterized as fragile or critically sensitive to desertification, with human activities playing a significant role. The non-proper changes of land use, overgrazing and overexploitation of water resources are only some of these activities. The eastern part of Crete was found to be more sensitive to desertification than the western part mainly due to the climate conditions (lower mean annual precipitation). Based on the results, 37% of the area of Crete is characterized as critically sensitive to desertification. Moreover, areas prone to desertification seem to be clustered more in the eastern part of the island. In addition, the majority of the intensive agricultural regions on Crete consist of areas critically sensitive to desertification. Based on the main factors affecting environmental sensitivity to desertification, mitigation measures should be taken. The resulting maps show that a small decrease in the quality of one of these factors (e.g. climate change, land use intensity) can produce very critical conditions. The ESAI maps could become a valuable tool for local authorities in order to apply policies for the prevention and mitigation of desertification in the Mediterranean region.

ACKNOWLEDGEMENTS

With the contribution of the LIFE + financial instrument of the European Union to project LIFE14 CCA/GR/000389 – AgroClimaWater.

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