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Soil Degradation Processes,
Causes, and Assessment
Approaches
Nada Dragovićand Tijana Vulević
Faculty of Forestry, University of Belgrade,
Belgrade, Serbia
Definitions
Soil
degradation
is an element of the land
degradation process and refers
to a decrease in soil’s
productivity and quality.
Soil erosion is a soil degradation process
defined as displacement of
topsoil from land surface
through water, wind, or tillage.
Salinization is a soil degradation process that
refers to the degradation of land
through salt accumulation. It is a
natural process or human
induced through irrigation and
land clearing, in which case it is
called secondary salinity.
Soil
contamination
is the chemical degradation
caused by presence of harmful
substances resulting from
activity such as waste disposal,
mining, oil extraction, and
military or nuclear activities.
Soil sealing is a permanent covering of land
and its soil with impermeable
artificial material, such as
asphalt and concrete.
Soil organic
matter
is a complex mixture of organic
material (plants, plant tissue,
microorganisms or animals) at
different stages of
decomposition due to both
abiotic and biotic processes.
Introduction
Land degradation refers to a loss of or reduction in
the productivity of the land, which arises as a
result of various natural processes, often acceler-
ated by an anthropogenic perturbation (Lal 1993).
The most significant causes of land degradation
are land use, climate change, overpopulation, and
urbanization.
Land degradation leads to a reduction in
soil quality and a decrease in a future potential
for the survival of living organisms (Fitzpatrick
2002). It is a global threat with three distinct
categories: natural degradation, human-induced
degradation, and desertification. Induced
degradation results from inappropriate land use
and management and occurs more rapidly than
natural degradation (Fitzpatrick 2002). The
most severe degradation form is desertification,
which occurs in drylands covering about 40%
of the world’s land surface (UNEP 1992). Land
degradation has both on-site and off-site effects.
© Springer Nature Switzerland AG 2020
W. Leal Filho et al. (eds.), Life on Land, Encyclopedia of the UN Sustainable Development Goals,
https://doi.org/10.1007/978-3-319-71065-5_86-1
On-site effects are experienced directly where
degradation occurs (a reduction in the productive
capacity of land), whereas off-site effects occur in
the surrounding areas (flooding, sedimentation, a
water quality decline) (FAO 2011; Stringer 2017).
Land degradation has a wider scope than soil
degradation, which refers to a decline in soil qual-
ity and productivity. The speed of the soil degra-
dation process depends on natural factors
(characteristics of soil, climate, and vegetation)
and anthropogenic factors (land use, soil manage-
ment, and farming/cropping system) (Lal 2001).
More than 75% of land in the world is
degraded (Gibbs and Salmon 2015). The five
global assessments of soil degradation carried
out between 1977 and 2003 estimated that global
degradation ranges between 15% and 63%,
whereas for dryland degradation, the range is
from 4% to 74% (Safriel 2007).
Human-induced soil degradation affects an
area of 1,965 million ha worldwide (Oldeman
et al. 1991). Table 1details the global extent of
degraded land surface due to water erosion, wind
erosion, and chemical and physical degradation,
obtained using the GLASOD map.
According to the world map of human-induced
soil degradation, severely degraded countries are
mostly located in Africa (Swaziland, Angola,
Gabon, Congo, Equatorial Guinea, and Zambia)
and Asia (Bhutan, Thailand, Indonesia, Republic
of Korea, Laos, and Malaysia) (Bai et al. 2008).
In Africa, land degradation affects 2/3 of the
territory, from humid zones to arid and semiarid
zones, and about 485 million people (ECA 2007).
Oldeman et al. (1991) estimated that 494 million
ha of the land in Africa is affected by human-
induced soil degradation.
Asian countries face many of the problems of
soil erosion, soil salinization, an increasing popu-
lation and pasture and vegetative degradation.
Asia is the continent that is threatened most by
human-induced soil erosion, with an affected area
of 748 million ha (Oldeman et al. 1991). Together,
Africa and Asia account for more than 55% of all
global drylands (Reynolds et al. 2007). The Asian
countries which are the most vulnerable to desert-
ification are Afghanistan and Pakistan (Eswaran
et al. 2001).
The main drivers of soil degradation in
Western and Northern Europe are surface sealing
through urbanization and infrastructure develop-
ment, whereas in Southern and Central Europe,
the main driver is water erosion (EEA 1999).
In Southeastern Europe, soil is threatened by
degradation processes, the most common of
which is soil erosion caused by water (GIZ
2017). Panagos et al. (2015) estimate that the
highest rates of soil erosion in the EU countries
Soil Degradation Processes, Causes, and Assessment Approaches, Table 1 The global extent of human-induced
soil degradation. (Modified from Oldeman et al. 1991)
Region
Land surface
(10
6
ha) Land surface affected by different types of soil degradation (10
6
ha)
Total Degraded
Water
erosion
Wind
erosion
Chemical soil
degradation
Physical soil
degradation
Africa 2,966 494 227 186 62 19
Asia 4,256 748 441 222 74 12
South
America
1,768 243 123 42 70 8
Central
America
306 63 46 5 7 5
North
America
1,885 96 60 35 –1
Europe 950 218 114 42 26 36
Oceania 882 102 83 16 1 2
World 13,013 1965 1,094 548 240 83
“–” indicates that an eligible area is affected by the specific degradation process
2 Soil Degradation Processes, Causes, and Assessment Approaches
are in the Mediterranean and Alpine countries,
such as Italy, Greece, and Austria, due to high
rainfall erosivity and steep slopes (Table 2).
The Food and Agriculture Organization and
the Intergovernmental Technical Panel on Soils
indicate that 14% of global land degradation
occurs in Latin America and the Caribbean region,
with water erosion, organic carbon losses, and
salinization the main drivers of land degradation
(FAO and ITPS 2015).
The most widespread processes that lead to the
degradation of land and soil resources are physi-
cal, chemical, biological, and natural processes
(Johnson and Lewis 2007). Physical processes
include a decline in the soil structure, leading to
crusting, compaction, erosion, desertification, and
environmental pollution, whereas chemical pro-
cesses include a loss of nutrients and/or organic
matter, acidification, salinization, and pollution
(Oldeman et al. 1991; Eswaran et al. 2001).
Important among biological processes are a
decline in land biodiversity and a reduction in
both the total and biomass carbon levels
(Eswaran et al. 2001).
This chapter includes sections related to the
causes and types of soil degradation and different
assessment methods and provides future guide-
lines for soil degradation prevention.
Causes of Soil Degradation
There are many factors contributing to soil degra-
dation, among which the most recognized are
deforestation, shifting cultivation, overgrazing,
monocropping, and the use of agrochemicals.
Deforestation. The main natural causes are
fires and floods and among human activities the
causes are logging, timber production, the conver-
sion of a forest into agricultural land, and urban-
ization. The effects of deforestation are numerous:
a loss of species, increased carbon emission or
increases in the greenhouse effect, flooding, and
soil erosion.
Shifting cultivation. It is an old farming prac-
tice, where the “slash-and-burn”technique is
applied to clear land, followed by a long fallow
period important for the restoration of soil fertility.
Many studies indicate that crop burning has harm-
ful effects on soil, such as an increased suscepti-
bility to soil erosion and a reduction in nutrients.
A better alternative is “chop-and-mulch,”i.e., the
cutting of the plants (crops) that are then used as
mulch. This significantly increases the concentra-
tion of nutrients and the content of organic matter
(FAO and UN 2015).
Overgrazing. It is intensive grazing that leads
to a significant disturbance of the growth, quality,
and composition of vegetation. Grasslands with
the high pressure of livestock lose vegetation
cover and, therefore, fertility of the soil, which
becomes susceptible to erosion. Numerous studies
have shown that during overgrazing, there is a
change in soil moisture, organic matter, nitrogen
content, and microbial activity. The total carbon in
the soil is permanently reduced by 12% due to
overgrazing over a period of 40 years (Li et al.
1997). This is also the cause of soil erosion and
desertification.
Monocropping and use of agrochemicals.
Many crops widespread throughout the world
(wheat, corn, rice) have been cultivated as a
monoculture for many years on the same soil, in
the absence of crop rotation. Over a long period of
time under the same culture, a soil loses nutrients
and its resistance to insects and pests is reduced,
so farmers are forced to use pesticides in order to
provide the required yield. The use of artificial
fertilizers, pesticides, and other chemicals intro-
duces heavy metals and often very toxic
chemicals into the land. Their nonselective and
excessive use has a permanent negative effect on
the quality of soil and represents one of the most
significant forms of degradation (Osman 2014).
In addition, other causes of soil degradation
include the mismanagement of irrigation, the use
of heavy agricultural machinery, mining, war, or
indiscriminate waste disposal.
Types of Soil Degradation
Soil degradation is classified in many ways in the
literature. The Global Assessment of Soil Degra-
dation (GLASOD) recognizes four major types of
soil degradation: water erosion, wind erosion,
Soil Degradation Processes, Causes, and Assessment Approaches 3
chemical deterioration (including organic matter
decline, salinization, acidification, and pollution),
and physical deterioration (such as compaction,
sealing, waterlogging, and urbanization).
Soil erosion is considered to be the main and
the most widespread form of land degradation.
Soil erosion is caused by the activity of water
and the wind and represents the detachment and
movement of soil particles from one place to
another. This process can be natural or accelerated
by human activity. It depends on many factors,
among which the most important are the configu-
ration of the terrain (slopes) and climatic-
meteorological conditions. Soil erosion is most
pronounced on steep terrain, where soil material
is easily transported by water (Fig. 1). The most
common types of erosion are splash erosion, sheet
erosion, rill erosion, and gully erosion (Osman
2014).
The global loss of soil due to water erosion
amounts to 20–30 billion tons per year, which is
equivalent to a loss of land use of 1 m on an area of
13,300 to 20,000 km
2
per year (FAO and UN
2015). Soil losses caused by wind erosion are
estimated at 2 billion tons annually, whereas soil
losses caused by tillage are estimated at 5 billion
tons per year. To date, established tolerant land
losses have only beset as short-term goals. A long-
term goal should be that the degree of degradation
of agricultural land leads to a zero level (UN,
Sustainable Development Goals –15.3 Land
Degradation Neutrality).
Numerous studies, including FAO, have esti-
mated the costs of soil erosion. According to
Fitzpatrick (2002), direct and indirect annual
costs due to erosion can be up to 400 billion
dollars worldwide. This represents a cost of
approximately $80 a year for every person on
Earth due to soil erosion.
In order to avoid or mitigate water erosion,
different biological, technical, biotechnical, and
agro-technical measures could be taken. The
most common technical work for water erosion
mitigation is check dam construction (as a single
object or as a series of transverse structures on the
riverbed (Fig. 2). In order to reduce wind erosion,
measures based on a reduction of the wind force
or an increase in soil surface resistance are used
(a wind barrier, crop covers, the stabilization of
soil, ridging and surface roughening, residue man-
agement, and strip cropping).
Organic matter decline occurs due to the inad-
equate use and treatment of soils. Organic matter
is important not only for soil fertility but also for
Soil Degradation Processes, Causes, and Assessment Approaches, Table 2 Soil loss due to erosion and urban-
ization. (Source: Panagos et al. 2015; EEA 2010)
Country
Average soil loss rate
[t ha
1
y
1
]
% of the total soil loss in
the EU
a
Loss of agricultural land due to
urbanization [ha]
Austria 7.12 5.65 11,019.37
Belgium 1.22 0.30 18,980.81
Czech
Republic
1.65 1.24 11,279.58
Germany 1.25 4.15 206,362.4
Estonia 0.21 0.09 2,544.03
Spain 3.94 19.61 174,213.9
France 2.25 11.85 138,564.4
Greece 4.13 5.31 35,762.2
Hungary 1.62 1.42 10,211.72
Ireland 0.96 0.55 32,052.14
Italy 8.46 24.13 82,511.21
Lithuania 0.52 0.32 729.4122
Luxembourg 2.07 0.05 1,830.784
Latvia 0.32 0.20 115.7548
a
a loss of agricultural soil due to urbanization between 1999 and 2000, based on an analysis of CORINE land cover
4 Soil Degradation Processes, Causes, and Assessment Approaches
the structure, aeration, infiltration, water retention
capacity, and soil biodiversity (Montanarella
2007). It serves as a soil acidity puffer and a
source of energy for soil microorganisms as
well. Organic carbon is the most important com-
ponent (about 58%) of organic matter and soil
quality indicators (Young et al. 2015). Significant
carbon losses arise from activities that lead to the
Soil Degradation Processes, Causes, and Assessment Approaches, Fig. 1 Intensive erosion on the steep slopes of
Stara Planina (Old Mountain), Eastern Serbia, caused by deforestation. (Author: Dragović2007)
Soil Degradation Processes, Causes, and Assessment Approaches, Fig. 2 (a) A single concrete check dam
constructed for sediment deposition, Salzburg, Austria, (b) a series of concrete check dams for slope and water energy
reduction, Tyrol, Austria. (Author: Dragović2008)
Soil Degradation Processes, Causes, and Assessment Approaches 5
transition from natural to agricultural ecosystems
(the destruction of forests, the burning of biomass,
etc.) (Lal 1993). The global total of organic and
inorganic carbon in soil is estimated at 1,500
Gt. According to research conducted at the Joint
Research Centre (Italy), 45% of the land in Europe
has a low or very low content of organic carbon.
Agricultural production has further aggravated
land degradation, which has contributed to an
estimated loss of between 42 and 78 billion tons
of carbon, mainly emitted into the atmosphere as
carbon dioxide and other gasses, with a negative
effect on climate change and food production
during the past century (Lal 1993). Small changes
in organic carbon in soil have major consequences
for the concentration of carbon dioxide in the
atmosphere, because its volume in soil is three
times higher than in the atmosphere. The practice
of improving organic matter involves growing
cover crops and can have huge benefits for soil
(soil erosion reduction and the prevention of
leaching nutrients). In addition, the balanced fer-
tilization increases crop yields, and there are
increased amounts of organic residues returned
to soil (FAO 2005).
Salinization is one of the most widespread
forms of soil degradation and occurs in arid and
semiarid areas, where the amount of precipitation
is small and irrigation is applied without a proper
drainage system. However, salinization can occur
in all climatic areas if irrigation is irregularly
applied and is a result of natural (primary) and
human-induced (secondary) processes (FAO and
UN 2015). The degradation caused by salinization
is believed to have affected a total area of about
62 million hectares, with estimated global losses
of around 27.3 billion USD per year, over the last
two decades (Qadir et al. 2014). According to the
EEA (1995), salinization occurs and negatively
affects 3.8 million hectares in Europe, with
the most endangered parts in Italy, Spain and
Hungary, among others.
According to Montanarella (2007), the most
significant consequences of salinization are a
loss of soil fertility, a reduction in water infiltra-
tion, a loss in biodiversity, damage to the infra-
structure, and the weakening of soil, to name but a
few. The negative effects of salinization can be
significantly mitigated by improved water man-
agement (irrigation and drainage), a better use of
fertilizers and the application of adaptive cultures.
In some areas it is necessary to consider the pos-
sibility of land use change and the conversion of
soil into cultivated land (Young et al. 2015).
Soil contamination results from industry, min-
ing, illegal landfills and poorly managed landfills,
the storage of chemicals, accidental or intentional
chemical spills, the disposal of hazardous mate-
rials, and military activities. There is no relevant
data about the assessment of soil contamination
parameters (the total pollution area, the type of
pollutant, the number of inhabitants exposed to
contamination, environmental damage, etc.) for
countries in the world because there is no common
methodology for their assessment (Montanarella
2007). According to Montanarella (2007), the
most significant consequences of contamination
are a risk to health for the people living in the
environment of the polluted area, the contamina-
tion of surface waters, the contamination of
groundwaters, a loss of biodiversity and biologi-
cal activity, and a loss of soil fertility due to
disturbance of the nutrient cycle. The European
Environment Agency (EEA) estimates that 60%
of Europe’s land is polluted by industrial activi-
ties. Among the most common harmful pollutants
are heavy metals (37%) and mineral oils (33%).
The number of contaminated sites equates to one-
third of the countries of the European Union, with
the highest number of monitored contaminated
sites (422) in Serbia (GIZ 2017). The polluted
soil remediation options are classified into biolog-
ical, chemical, or physical and may be applied
either in situ (using barriers on-site in order to
prevent the movement of pollutants) or ex situ
(treating the excavated soil off-site) (Scullion
2006).
Other Types of Soil Degradation
Acidification, like salinization, is a severe form
of degradation that results in a reduction in the
agricultural land production potential. The acidi-
fication process prevents plants using water,
resulting in drying and erosion, and causing an
6 Soil Degradation Processes, Causes, and Assessment Approaches
increased leaching of nutrients and an irreversible
breakdown of silicate minerals in the soil
(Fitzpatrick 2002). Soil acidity is a natural process
that can be accelerated by human activity and is
particularly pronounced in areas with less precip-
itation. Acid soil management involves monitor-
ing the soil pH, understanding the tolerance of
crops and pastures to acidity and treating surfaces
with neutralizers in order to prevent acidity.
Soil compaction is caused by long-term pres-
sure on the surface, brought about by the activity
of heavy mechanization in processing agricultural
land (Kertész 2009), or due to a high grazing
intensity and the resulting grazing pressure of
livestock. The effects of soil compaction are a
loss of soil fertility due to structural change, a
reduction in the infiltration capacity of the land,
an increased sensitivity to erosion, and a loss of
the biodiversity of the land. Some measures that
may prevent or reduce soil compaction are the
application of a conservation tillage system, the
control of and a reduction in vehicle traffic, and
the avoidance of using oversized equipment
(Raper and Kirby 2006).
Soil sealing involves covering the soil surface
with an impermeable material. The main reasons
for soil sealing are urbanization, an increase in
the traffic infrastructure and a migration of the
population (Montanarella 2007). It occurs to the
detriment of agricultural land (Table 2). The
highest sealing rate of 16–20% is recorded
in European countries (Belgium, Denmark, and
the Netherlands) due to population growth and
industrial development (Kertész 2009). The
consequences of soil sealing are an increase in
the risk of floods, the disruption of water and
gas flows, a reduction in groundwater, water
pollution, and the loss of both land and land
biodiversity. One of the most common soil sealing
mitigation measures is using highly permeable
materials and surfaces, a green infrastructure and
water harvesting (European Commission 2012).
Desertification
Many authors consider desertification an
equivalent to degradation in arid and subarid
areas, while others identify desertification as a
particular type of soil degradation, given the fact
that it may appear as a higher form of degradation
in moderately humid or humid tropical
areas (Eswaran et al. 2001). Both terms mean a
permanent loss of land productivity. About 33%
of the global area is estimated to be susceptible
to desertification. Desertification is present in
Africa, several Asian countries, and South
America, but it has also become a problem in
the United States, Australia, and Southern
Europe; in fact desertification is a problem in
about 100 countries across all five continents,
affecting over 2 billion people. Due to desertifica-
tion, about 12 million hectares of land for pro-
cessing are lost each year. The major global
problem caused by desertification is a loss of the
biological and economic productivity of land
(EU 2011). The main cause of desertification is
overgrazing. The consequences of desertification
are a reduction in yield or crop failure, floods, a
reduction in water quality, hunger, and poverty,
to name but a few. Based on the United Nations
Convention to Combat Desertification (UNCCD),
which came into force in December 1996, many
recommendations have been made to reduce the
desertification process (Safriel 2007). Some of the
measures to be applied in order to combat desert-
ification are as follows: introducing policies for
changing land use patterns and the methods for
cultivating agricultural crops, educating the pop-
ulation, and introducing new soil technologies
including improved water management and the
application of good practices.
Soil Degradation Assessment
The need for assessing soil degradation by using
different methods based on expert opinion, land
users’opinions, modelling, field observation,
Soil Degradation Processes, Causes, and Assessment Approaches 7
monitoring and measurement, remote sensing,
and GIS has been recognized since the early
1930s (Kapalanga 2008).
The assessment of soil degradation depends on
the type of degradation process, the scale of the
assessment, and a method that can be based on an
expert opinion (through questionnaires), remote
sensing (satellite imaginary), or modelling.
According to Caspari et al. (2015), the following
approaches can be distinguished:
(a) The expert-based approach is used because
of a lack of reliable data regarding soil and
land degradation, some advantages being the
best local knowledge is included in the assess-
ment; land degradation causes, types, degrees,
and extents can be assessed on multiple
scales; and it contributes to raising awareness,
thus being a supportive collaboration and a
form of information sharing. The limitations
of this approach are its subjective nature and
the fact that the gathered data may not always
be up-to-date.
(b) The remote sensing approach, based on
the use of satellite imaginary, attracts huge
interest. Compared to the expert-based
approach, this approach enables the rapid
acquisition of up-to-date information across
a large area in a homogeneous manner. A lot
of approaches to soil degradation assessment
are based on remote sensing (GLASOD,
ASSOD, SOUVER), but the reason remote
sensing is used for soil degradation assess-
ment on a small scale is due to the
unavailability of extensive ground data nec-
essary for reliable estimates (Kniivila 2004).
(c) The modelling approach is widely applied in
order to assess different types of degradation.
The dominant type of degradation in Europe
is water erosion, which is assessed by
using different models: models based on the
Universal Soil Loss Equation (USLE), the Pan
European Soil Erosion Risk Assessment
(PESERA), statistical regression-based
approaches, and factor scoring methods
based on expert knowledge (Mantel et al.
2014). To predict the risk of degradation,
these models use the geographical informa-
tion system (GIS).
Until the late 1990s, land degradation assess-
ment was mainly focused on drylands. The major
land and soil degradation assessments of the past
are as follows:
•Global Assessment of Human-Induced Soil
Degradation –GLASOD (1987–1990)
•1st edition of World Atlas of Desertification –
WAD1 (1992)
•Assessment of Soil Degradation in South and
Southeast Asia –ASSOD (1995–1997)
•The World Overview of Conservation
Approaches and Technologies –WOCAT data-
base (1992)
•Mapping of Soil and Terrain Vulnerability in
Central and Eastern Europe –SOVEUR
(1997) 2nd
•2nd edition of World Atlas of Desertification –
WAD2 (1997)
•The Millennium Ecosystem Assessment –
MEA (2001–2005)
•Land degradation assessment in Drylands pro-
ject –LADA (2006)
•Global Assessment of Land Degradation and
Improvement –GLADA (2006–2009)
•Global Land Degradation Information
System –GLADIS (2009–2011)
A comparison between the three soil degrada-
tion assessment methodologies initiated by the
International Soil Reference and Information
Centre (ICRIS) is presented in Table 3. GLASOD,
ASSOD, and SOVEUR are the qualitative soil
degradation assessment methodologies that use
information based on expert knowledge and an
existing database so as to provide maps of the
degradation type, extent, degree and rate, and its
main causes.
The distribution of the main degradation types
in South and Southeast Asia, using the GLASOD
and ASSOD methodologies, is given in Table 4.
According to both assessment approaches, water
erosion is the dominant degradation type.
8 Soil Degradation Processes, Causes, and Assessment Approaches
One of the newly assessment of global land and
soil degradation is the third edition of the World
Atlas of Desertification (WAD3), which is being
compiled by the Joint Research Centre (JRC) of
the European Commission, in partnership with the
United Nations Environment Programme (UNEP)
(Caspari et al. 2015). This method uses the Nor-
malized Difference Vegetation Index (NDVI)to
assess land degradation. A variety of studies
conducted until now have used different indica-
tors of land degradation, such as land cover data,
NDVI index, net primary production (NPP), soil
erosion state, and soil moisture index.
There are many actions and agreements
designed to avoid or reduce land degradation,
some of them being the United Nations Conven-
tion to Combat Desertification (UNCCD), the
United Nations Framework Convention on
Climate Change (UNFCCC), the Convention on
Biological Diversity (CBD), the Convention on
Wetlands of International Importance, and the
2030 Agenda for Sustainable Development with
Sustainable Development Goals (SDGs) where
SDG 15 makes an explicit reference to land
degradation neutrality (LDN) (UN 2015). To
monitor the realization of SDGs, the Global
Indicator Framework (UN 2017) was adopted,
which is updated every year. The Global Indicator
Framework includes 231 indicators. Within SDG
15, 14 indicators have been identified, including
an indicator called “the proportion of the land
Soil Degradation Processes, Causes, and Assessment Approaches, Table 3 Comparison of soil degradation
assessment methodologies. (Source: Lynden et al. 2004)
GLASOD ASSOD SOVEUR
Coverage Global South and Southeast Asia
(17 countries)
Central and Eastern Europe
(13 counties)
Scale 1:10 M 1:5 M 1:2.5 M
Base map Units loosely defined
(physiography, land
use, etc.)
Physiography, according to the
standard SOTER methodology
Physiography and soils, according
to the standard SOTER
methodology
Status
assessment
Degree of
degradation and
extent classes
Impact on productivity and extent
percentages
Degree(the intensity of the process),
impact on productivity, and extent
percentages
Rate of
degradation
Limited data Greater importance As with ASSOD
Conservation No conservation data Some conservation data No conservation data
Detail Data not on a country
basis
Data available per country Data available per country
Cartographic
possibilities
Maximum
2 degradation types
per map unit
More degradation types defined, no
restrictions on the number of types
per map unit
As for ASSOD, but a special
emphasis on pollution
Source Individual Experts National institutions National institutions
Soil Degradation Processes, Causes, and Assessment Approaches, Table 4 The distribution of the main degra-
dation types in South and Southeast Asia. (Modified by Lynden and Oldeman 1997)
% of the total degraded area
GLASSOD (%) ASSOD (%)
Physical deterioration 0.5 9.2
Chemical deterioration 7.0 4.3
Wind erosion 19.9 19.8
Water erosion 72.7 46.7
Soil Degradation Processes, Causes, and Assessment Approaches 9
degraded over the total land area,”which refers to
the restoration of degraded land and soil.
Conclusions
Land degradation is a natural or human-induced
process affecting more than 75% of the world’s
land. It refers to the decline of the entire ecosys-
tem’s ability to provide goods and services and
has three categories: natural degradation, human-
induced degradation, and desertification.
Soil degradation is a form of land degradation
that refers to loss of soil quality and productivity.
It can occur as a natural process caused by
the inherent characteristics of the soil, climate,
and topography. Human-induced degradation
develops more rapidly than natural degradation
and can be reduced or avoided by regulating
human interventions such as deforestations, over-
grazing, and mismanagement of agricultural land.
The causes of soil degradation that are human
driven include overgrazing, shifting cultivation
and monocropping, and the use of agrochemicals,
while deforestation can present either as a natural
or human-driven loss of trees.
Soil erosion by water is the main and most
widespread form of soil degradation globally,
leading to soil loss, increased pollution, and sed-
imentation in rivers. The key soil erosion control
measures include the maintenance of a protective
cover (trees, mulches, and crops), the selection of
optimal land use, and the construction of technical
works (e.g., check dams) on the riverbed.
Besides soil erosion, soil sealing and soil con-
tamination are the main problem for EU soils. Soil
sealing comprises a permanent covering of land
and its soil with impermeable artificial material
(asphalt and concrete) and is a result of urbaniza-
tion and infrastructure development.
Soil contamination is the chemical degradation
of soil that involves the presence of harmful sub-
stances in the soil as a result of industrial
activities, mining, nuclear activities, or improper
disposal of waste. Remediation options include a
variety of physical and chemical treatments of soil
in place (in situ) and after excavation (ex situ).
Salinization is a widely present type of
chemical soil degradation that occurs in arid and
semiarid areas (mostly in Asia), causing soil
infertility, a reduction in water infiltration, loss in
biodiversity, and damage to the infrastructure.
The expansion of salt-affected soil could be
reduced by applying appropriate irrigation prac-
tices, better use of fertilizers, or land use change.
Soil organic matter (SOM) is considered an
indicator of soil degradation. Soils containing
more organic matter have better structure,
increased water infiltration, and they are less sus-
ceptible to compaction, erosion, and
desertification.
To prevent soil degradation processes that lead
to the deterioration of soil chemical, physical, and
biological properties, it is necessary to monitor
and assess soil degradation processes using appro-
priate methods (expert-based, remote sensing, or
modelling). Identification of the degradation type
is important to define all consequences and, thus,
the expected cost of soil degradation mitigation
measures. It is important to be aware that several
degradation processes could occur simulta-
neously, or one type of process could directly
cause the occurrence of another (e.g., the occur-
rence of deforestation could lead to soil erosion
and ultimately cause an increased risk of flood).
The spatial extent, degree, and rate of degradation
type should be a base for the decision-making
process regarding the best sustainable land man-
agement (SLM) practice that should be applied.
Some challenges are related to the better mon-
itoring and assessment of soil degradation. It is
necessary to close data gaps, enable access to data
and data comparability, gather more on-the-
ground information, and take into account the
uncertainty of the future.
The selection of an investment solution and a
capacity building approach to support the imple-
mentation of EU SDG 15 is crucial. The involve-
ment of different ministries, departments, and
agencies with adequate communication and coop-
eration is required, as is citizen participation in the
implementation of the SDGs. There is a need for
taking actions at local and sub-national levels, and
implementing policies and programs at national
and regional levels that can prevent or reverse
10 Soil Degradation Processes, Causes, and Assessment Approaches
land degradation. In addition, the global popula-
tion has to reduce pressure on the environment by
reducing its demands and economic activities.
Cross-References
▶Human-Induced Soil Degradation
▶Land Degradation and Climate Changes
▶Land Degradation Neutrality
▶Land Management
▶Soil Quality
▶United Nations Convention to Combat
Desertification (UNCCD)
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