The Global Problem of Land Degradation and Desertification 19 Hungarian Geographical Bulletin 2009. Vol. 58. No 1. pp. 19–31. The global problem of land degradation and desertifi cation Ádám Kertész1 Abstract It’s a well known fact that land(scape) degradation is an ensemble of negative processes extending over immense areas. The methodologies of physical and social geography are the best tools for the investigation of land degradation processes, due to the complex nature of these processes. It is well known that environmental factors contribute to land degradation processes. Socio-economic factors and the role of human society is equally important, and in some cases, even more important, than natural factors. Degradation processes within subhumid, semi-arid and arid areas are defi ned as desertifi cation processes to draw att en- tion to the specifi c dangerous situation in these areas. Hungary signed the Convention on Desertifi cation, as increasing aridity is a real national danger, especially on the Danube- Tisza interfl uve. There are areas in Hungary corresponding to desertifi cation defi nitions. Thus, desertifi cation research is an important challenge for Hungarian geography. Key words: water erosion, land degradation, desertifi caton, Danube–Tisza interfl uve Introduction The degradation of the Earth’s surface (i.e. land degradation) is one of the most severe problems of our times. The concept of land degradation originates from soil degradation and it is oft en used as a synonym for soil degradation. It is evident that if soil is degraded it has huge impacts on both the land and landscape, because soil degradation prevents or impedes plant growth. Land and soil are not identical notions, but they are oft en used interchangeably. To avoid this confusion, I propose to use the term ‘landscape degradation.’ Landscape degradation means much more than just the degradation of the uppermost layer of the Earth’s crust. It means the decline of all landscape forming factors and of their synthesis, which is called landscape in physical geography and landscape ecology. Landscape ecology and physical geogra- phy deal with various aspects of landscape development (Tóth, A.–Szalai, Z. 2007). However, despite its importance, few scientifi c papers in Hungary report degradation processes. ¹ Geographical Research Institute, Hungarian Academy of Sciences. H-1112 Budapest, Budaörsi út 45. E-mail: kertesza@helka.iif.hu 20 Soil degradation processes Soil degradation processes are grouped in diff erent ways by various authors. A more practical classifi cation is presented below (EEA Environmental As- sessment Report 2003). (1) Soil sealing. It is not by accident that soil sealing is given fi rst place amongst soil degradation processes. Soil sealing is the result of construction activities (including roads, railways and buildings). Due to soil sealing, the soil does not function properly, as it has no contact with the atmosphere and is devoid of vegetation. On the sealed soil surface, water runs off without being fi ltered, with increased velocity and volume. The highest share of sealed soil surface (16–20%) is in Belgium, The Netherlands and Denmark. The share of sealed soil has been continuously growing within the EU. reaching an average value of 8–9% in 2000. (2) Soil erosion (Photo 1). In Europe water erosion is more important than wind erosion, but wind erosion also causes huge damage. As an example of the importance of wind erosion in the World we should remember that the establishment of the US Soil Conservation Service took place primarily because of the sand storms of the 1930s. Soil erosion risk and the damage caused by erosion are also very remarkable in Hungary (Jakab, G.–Szalai, Z. 2005). Photo 1. Gully erosion near Bergville, South Africa 21 (3) Soil contamination can originate from both diff use and local sourc- es. Contamination from the atmosphere, from running water or from the soil belong to the fi rst group. These processes may cause acidifi cation, eutrophica- tion and other severe damage. The direct application of chemicals (fertilizers, pesticides and sewage sludge), sometimes also containing heavy metals, are also diff use sources. Local contamination sources can be of diverse origins and are usually connected with industrial activity. (4) Salinization. Near-surface salt accumulation is present in several European countries, including Hungary. The most important areas aff ected by seashore, inland and secondary salinization due to irrigation are in the Mediterranean countries, Hungary and several countries of the former Soviet Union (Photo 2). (5) Soil compaction is the result of the activity of soil cultivating ma- chines. Subsoil compaction is an extremely damaging and is diffi cult to rectify. The fi rst World assessment of soil degradation is GLASOD (Global Assessment of Soil Degradation, Oldeman, L.R. et al. 1991), which assesses the following degradation processes: The extension of various forms of soil degradation water erosion – ▪ Photo 2. Saline spot on the Danube-Tisza Interfl uve, near Apajpuszta 22 wind erosion chemical degradation physical degradation. The rate of degradation Light Moderate Strong Extreme. The causes of degradation (deforestation, overgrazing, improper farm- ing, overexploitation, contamination). According to Oldeman, L.R. et al. (1991) 3.7% of the Earth’s surface is aff ected by physical and chemical degradation and 12% by water and wind erosion (Tables 1 and 2). Especially high is the proportion of physical and chemical degradation in Europe and in Central America and the share of the areas aff ected by soil erosion is also the highest here. Studying these tables, it is evident that soil degradation is a major problem in Europe. The concept of land degradation As mentioned above, land degradation means much more than the degra- dation of the land/soil. Because of the complex nature of land degradation processes it is essentially a geographical subject matt er. In this paper, land degradation will be discussed from the perspective of physical geography. However, land degradation can result from both physico-geographical and socio-economic causes. An evident example is overpopulation of humans and animals launching well-known degradation processes. The investigation of land degradation processes together with land use change studies represent the most up-to date and innovative research trends in modern geography. According to Barrow, C.J. (1991) it is impossible to give a precise defi - nition of land degradation. It may be defi ned “as the loss of utility or the re- duction, loss or change of features or organisms which cannot be replaced” (Barrow, C.J. 1991). The land is degraded when “it suff ers a loss of intrinsic qualities or a decline in its capabilities” (Blaikie, P.–Brookfield, H. 1987). The UNEP (1992) defi nition emphasized the reduction of the potential of natural resources as a result of processes acting in the landscape. Johnson, D.L.–Lewis, L.A. (1995) underlined the role of human interventions in land degradation and focused on the reduction of biological production and/or utility of an area. Distilling the essence of these cited defi nitions, it is evident that there are common elements in them. Hence, even thought it is diffi cult to give a precise defi nition acceptable to all disciplines, the concept of land degrada- tion is fairly clear. It means the reduction or loss of biological productivity ▪ ▪ ▪ – ▪ ▪ ▪ ▪ – 23 Ta bl e 1. G lo ba l e xt en t o f c he m ic al a nd p hy si ca l s oi l d eg ra da ti on , b y re gi on (O LD E M A N , L .R . et a l. 19 91 ) R eg io n C he m ic al ly d eg ra d ed a re a P hy si ca lly d eg ra d ed a re a Total degraded area Total degraded land as % of total land used Loss of nutri- ents Salinization Pollution Acidifi cation Compaction, sealing and crusting Water-log- ging Loss of or- ganic matt er (m ill io n he ct ar es ) A fr ic a A si a So ut h A m er ic a C en tr al A m er ic a N or th A m er ic a E ur op e A us tr al ia W or ld 45 15 68 4 – 3 + 13 6 15 53 2 2 + 4 1 77 + 2 – + + 19 – 21 1 4 – – + + – 6 18 10 4 + 1 33 2 68 1 + 4 5 – 1 – 11 – 2 – – – 2 – 4 81 86 78 12 1 62 3 32 3 4, 8 3, 0 5, 1 6, 0 + 7, 7 – 3, 7 T he „ +” s ig n m ea ns n eg lig ib le , t he „ –” s ig n m ea ns n on e re po rt ed . Ta bl e 2 G lo ba l e xt en t o f s oi l d eg ra da ti on d ue to e ro si on , b y re gi on (O ld em an , L .R . e t a l. 19 91 ) R eg io n A re a er od ed b y w at er e ro si on A re a er od ed b y w in d e ro si on To ta l ar ea er od ed To ta l ar ea s e- ri ou sl y er od ed To ta l a re a se ri - ou sl y er od ed as a % o f t ot al la nd u se d L ig ht M od er at e St ro ng an d e x- tr em e To ta l L ig ht M od er at e St ro ng an d e x- tr em e To ta l A fr ic a A si a So ut h A m er ic a C en tr al A m er ic a N or th A m er ic a E ur op e O ce an ia W or ld 58 12 4 46 1 14 21 79 34 3 67 24 2 65 22 46 81 3 52 6 10 2 73 12 23 – 12 22 2 22 3 22 7 44 1 12 3 46 60 11 4 83 10 94 88 13 2 26 24 6 3 3 16 26 9 89 75 16 4 31 38 – 25 4 9 15 – 1 1 1 27 26 18 6 22 2 42 25 1 35 42 46 54 8 41 3 66 3 16 5 51 95 15 6 99 16 42 26 7 40 5 93 50 78 13 2 3 10 29 16 15 6 25 7 17 3 12 24 and negative eff ects on the functioning of the land and related ecosystems (Hudson, P.F.–Alcántara–Ayala, I. 2006). Functioning of the land involves the interaction of environmental factors and connections between landscape components, such as hillslopes and fl oodplains. These defi nitions and expla- nations show very clearly that land degradation is much more complex than soil degradation. Land degradation processes can have both natural and human (anthro- pogenic) origins. It is obvious that since the appearance of human beings on the Earth the importance of anthropogenic processes is enormous and has grown exponentially with time. Among natural processes, climate change is extremely signifi cant, considering that the rapid rate of climate change today is largely a human-induced process. However, most authors who have tried to defi ne land degradation restrict it to human-induced processes. In this sense, landscape development always involves degradation processes of natural origin, but these processes will then be compensated by the regenerating capacity of the landscape (Bádonyi, K. 2001). This approach excludes the infl uence of natural processes, such as natural climate change, natural catastrophes or geologic soil erosion. Global processes like global climate change, land use and land cover change, together with population increase, accelerate and increase land deg- radation. Especially, Third World countries suff er from degradation processes. In these countries overexploitation of natural resources in environmentally- sensitive areas also contribute to the acceleration of degradation processes. The eff ect of global warming on already degraded land also increases the intensity of degradation. According to Menshing, H.G.–Seuffert, O. (2001) it is very important that no irreversible damage occurs in the landscape due to improper land use. This is actually the application of the principles of sustainable development (i.e. the regenerating capacity and potential of the landscape should remain under the circumstances of any kind of land use or landscape use). As mentioned before, soil and land degradation are oft en used in- terchangeably (e.g. Imeson, A. C.–Emmer, I. 1992). Consequently, the salient processes of soil degradation and land degradation are identical (i.e. various processes of physical and chemical degradation belong to them). It is extremely important whether these processes are understood as landscape degradation or soil degradation processes. Some 38% of the agricultural area of the Earth can be considered as degraded (Fig. 1). Most of the areas in question are in the Third World (the share of degraded territories in Africa is 65%, in Central America 74% and in South America 45%). The proportion of degraded pasture and forests is much smaller (21 and 18%, respectively). Considering only used land (agricultural area, permanent pasture and forests; Table 3) the proportion of degraded area is 23% and that of strongly degraded land is 14%. 25 Table 3. Global estimates of soil degradation, by region and land use (sources: FAO 1990, Oldeman, L.R. et al. 1991 and Scherr, S.J. 1999) Region Agricultural land Permanent pasture Forests Total Degraded % Total Degraded % Total Degraded %(million hectares) (million hectares) (million hectares) Africa Asia South America Central America North America Europe Oceania World 187 536 142 38 236 287 49 1475 121 206 64 28 63 72 8 562 65 38 45 74 26 25 16 38 793 978 478 94 274 156 439 3212 243 197 68 10 29 54 4 685 31 20 14 11 11 35 19 21 683 1273 896 66 621 353 156 4048 130 344 112 25 4 92 12 719 19 27 13 38 1 26 8 18 Region All used land Total agricultural land, pasture and forests Degraded % Seriously de- graded % (million hectares) (million hectares) Africa Asia South America Central America North America Europe Oceania World 1663 2787 1516 198 1131 796 644 8735 494 747 244 63 96 218 104 1966 30 27 16 32 9 27 17 23 321 453 139 61 79 158 6 1216 19 16 9 31 7 20 1 14 Fig. 1. Estimates of soil degradation in the world, by region and land use (aft er FAO 1990, Oldeman, L.R. et al. 1991 and Scherr, S.J. 1999). 26 Desertifi cation processes Desertifi cation processes represent a special group of land degradation proc- esses. According to the United Nations Intergovernmental Convention to Combat Desertifi cation “Desertifi cation means land degradation in arid, semi- arid and dry sub-humid areas resulting from various factors including climate variation and human activities” (UNCOD 1977). The term ‘desertifi cation’ has emotional connotations and therefore its use is preferred to the term “land degradation.” It must be emphasized, however, that desertifi cation has a dif- ferent meaning than “desertation” (i.e. the formation of deserts). The concept of desertifi cation is much older than UNCOD. It dates back to the 1920s (Bovill, D.W. 1921, cited by Herrmann, S.M.–Hutchinson, C.F. 2005) when the extension of the West African Sahara into the Sahel zone was fi rst observed. The term ‘desertifi cation’ was fi rst used by Aubreville, A. (1949) to describe the change of productive land into a desert (Herrmann, S.M.– Hutchinson, C.F. 2005). According to this fi rst defi nition, the term desertifi cation is always connected with human activities (i.e. with land mismanagement). The Nairobi UNCOD Conference (United Nations Conference on Desertifi cation) in 1977 came about following extremely arid periods in Sahelian Africa. Climate change as a consequence of the greenhouse eff ect is a major global process. As it is the main factor infl uencing desertifi cation processes, the global importance of desertifi cation will increase and it is and it will be the most important group of land degradation processes in those regions of the world where there the climate is arid, semi-arid or dry subhumid. The atmospheric conditions of arid, semi-arid and subhumid climates are those that create large water defi cits, that is, where potential evapotranspi- ration (ETP) is much greater than precipitation (P). These conditions are evalu- ated by various indices. One of these is the FAO-UNESCO (1977) bioclimatic index: P/ETP. The threshold values of the bioclimatic zones are given below: Arid zone:0.03

5 0 50 –2 0 20 –5 <5 G ra ss la nd c on d it io n (% ) >7 5 50 –7 5 20 –5 0 <2 5 A ct ua l p ro d uc ti vi ty (% p ot en ti al ) 85 –1 00 65 –8 5 25 –6 5 <2 5 W at er e ro si on Su rf ac e st at us (% a re a) G ra ve l a nd s to ne s <1 0 St on es a nd b ou ld er s 10 –2 5 B ou ld er s an d r oc ks 25 –5 0 B ou ld er s an d r oc k ou t- cr op s >5 0 Ty pe o f e ro si on a E xp os ed s ub so il (% a re a) <1 0 10 –2 5 25 –5 0 >5 0 G ul ly a re a (% ) <1 0 10 –2 5 25 –5 0 >5 0 So il th ic kn es s (c m ) >9 0 90 –5 0 50 –1 0 <1 0 So il lo ss O ri gi na l s oi l d ep th < 1 m 25 25 –5 0 50 –7 5 >7 5 O ri gi na l s oi l d ep th > 1 m 30 30 –6 0 60 –9 0 >9 0 A ct ua l p ro d uc ti vi ty (% p ot en ti al ) 85 –1 00 65 –8 5 25 –6 5 <2 5 W in d e ro si on b A re a co ve re d b y hu m m oc ks (% ) <5 5– 15 15 –3 0 >3 0 Su rf ac e gr av el p er ce nt c ov er <1 5 15 –3 0 30 –5 0 >5 0 Sa lin iz at io n M or ph ol og yc So il el ec tr ic al c on d uc ti vi ty (m m ho s/ cm ) <4 4– 8 8– 16 >1 6 E xc ha ng ea bl e so d iu m (% ) <5 5– 20 20 –4 5 >4 5 C ro p yi el d (% p ot en ti al ) 85 –1 00 65 –8 5 20 –6 5 >4 5 A ff ec te d a re as (% ) <5 5– 20 20 –5 0 >5 0 a Sl ig ht : s lig ht to m od er at e in s he et e ro si on a nd r ill s. M od er at e: m od er at e to s ev er e in s he et e ro si on a nd r ill s. S ev er e: s ev er e in s he et e ro si on , r ill s an d g ul ly e ro si on . V er y se ve re : v er y se ve re in s he et e ro si on , r ill s an d g ul ly e ro si on . b In cl ud es s ev er al o f t he s am e ch ar ac te ri st ic s us ed fo r w at er e ro si on . c Sl ig ht : n o sa lt s. M od er at e: s al t s po ts . S ev er e: s al t s po ts a nd fi la m en ts . V er y se ve re : c ry st al lin e effl or es ce nc es a nd s al t c ru st s (s ol on ch ak ). 28 and wind erosion and salinization. Verón, S.R. et al. (2006) criticized the matrix from several perspectives, particularly the subjective nature of the data. Desertifi cation processes also aff ect Hungary, therefore Hungary is a signatory of the Desertifi cation Convention. It is interesting that even Iceland belongs to the countries suff ering from desertifi cation problems and research activities on the topic are remarkably advanced (Arnalds, O. 1997; Arnalds, O.–Kimble, J. 2001). The original concept of desertifi cation from the 1920s and 1940s is slightly diff erent from the UNCOD defi nition, which puts much more empha- sis on the formation of deserts and considers desertifi cation as a process lead- ing to desert development. According to Menshing, H.G.–Seuffert, O. (2001) we can describe a landscape desertifi ed only if geoecological characteristics of a landscape have already reached the representative values of the desert or these values will be reached within a certain period of time. Authors support- ing this concept of desertifi cation concentrate fi rst of all on marginal and zones surrounding deserts, which are especially sensitive to desertifi cation, as in the Sahara–Sahel marginal belt. There is continuous debate on the defi nition and understanding of desertifi cation (Bádonyi, K. 2001). All concepts agree upon the fact that desertifi cation means severe degradation problems of territories with water defi cits and ongoing aridifi cation. The main triggering factor of desertifi cation is usually the removal of natural vegetation by human society. This includes all forms of vegetation, not only forests, but also shrubs, weeds and grasses. Vegetation removal leads to climatic changes in the atmospheric boundary layer and increases aridifi ca- tion. Consequently, surfaces indurate, sometimes accompanied by crusting, and infi ltration rates decrease. Soil crusting and the lack of vegetation then exacerbates the destruc- tive eff ects of both water and wind erosion. Soil erosion removes the upper soil layers, which are usually rich in humus and nutrients, so reducing the feasibility of both vegetation re-establishment and agricultural land uses. Thus, landscape potential diminishes. The chance of reclaiming and regenerating vegetation in arid areas is less feasible if the climate is variable, especially if extreme events like extreme changes of moisture conditions are frequent (e.g. long periods of drought and catastrophic high intensity rainfall events). Reclaiming degraded, or desertifi ed land is an important issue in com- bating these processes (Mitchell, D.J. et al. 1998). Prevention, if at all possible, may even be more important than reclaiming already damaged land. Just one example of prevention against runoff and soil erosion is conservation agricul- ture or minimum tillage (Bádonyi, K.–Madarász, B. 2004). Desertifi cation is fi rst of all related to specifi c climatic conditions and vegetation destruction and consequent soil erosion. All physico-geographi- cal (environmental) factors contribute to desertifi cation, at least as modifying 29 agents. Relief, physical and chemical soil properties and soil parent material play important roles in the speed, rate and extent of desertifi cation. Desertifi cation rate depends also on initial soil moisture content and human interventions, and the latt er can be a positive interference. The course and consequences of the process are clear, from the initial status (i.e. subhu- mid, semi-arid or arid conditions) proceeding sequentially through the stages (e.g. if the area in question had a subhumid climate, then undergoing trans- formation to semi-arid and then arid conditions. As a consequence of ongoing aridifi cation the area may become hyperarid. In terms of vegetation, steppe will turn into savanna, followed by thorny savanna and then into semi-desert, reaching the ultimate stage of a desert. Conclusions Land (landscape) degradation is an ensemble of negative processes extend- ing over immense areas. The methodologies of physical and social geography are the best tools for the investigation of land degradation processes, due to the complex nature of these processes. It is well known that environmental factors contribute to land degradation processes. Socio-economic factors and the role of human society is equally important, and in some cases, even more important, than natural factors. Land degradation was fi rst appreciated by soil science as where the possibilities of agricultural use on degraded land are restricted or prevented because of soil degradation. Various forms of soil degradation are striking phe- nomena themselves, with saline areas being a good example. If the degraded area is not used for agricultural production, then the degradation of natural vegetation can also be striking. Land(scape) degradation processes are also present in Hungary, off ering a major challenge to Hungarian geography. Degradation processes within subhumid, semi-arid and arid areas are defi ned as desertifi cation processes to draw att ention to the specifi c danger- ous situation in these areas. The poorest regions of the Earth belong to here, totalling 40% of the Earth’s surface. These regions are continuously struggling with famine. There is debate about the defi nition of desertifi cation. Should the threshold values of the P/ETP index be taken literally, in which case the term desertifi cation does not refer to desert formation? Or should the defi nition re- late to the possibility of desert formation? Or it should it be restricted to those territories where the result of desertifi cation will or may really lead to desert conditions? Hungary signed the Convention on Desertifi cation, as increasing aridity is a real national danger, especially on the Danube-Tisza interfl uve. There are areas in Hungary corresponding to desertifi cation defi nitions. Thus, desertifi cation research is an important challenge for Hungarian geography. 30 Because of the complexity of the processes, future desertifi cation re- search should concentrate on revealing all environmental and landscape eco- logical aspects of the problem, aimed at presenting a full ecological synthesis of the landscape. Based on this synthesis, precise and practical suggestions should be developed on how to arrest land degradation, or how to redirect it towards positive directions, that is towards landscape reclamation and re- habilitation. REFERENCES Arnalds, O. 1997. Desertification in Iceland. Desertification Control Bulletin 32, pp. 22–24. Arnalds, O.–Kimble, J. 2001. Andisols of Deserts in Iceland. Soil Science Society of America Journal 65, pp. 1778–1786. Aubreville, A. 1949. Climats, forêts et désertifi cation de l’Afrique tropicale. Société des Editions Geographiques, Maritimes et Coloniales, Paris. Bádonyi, K. 2001. 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