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Iran has different climatic and geographical zones (mountainous and desert areas), mostly arid and semi-arid, which are suffering from land degradation. Desertification as a land degradation process in Iran is created by natural and anthropogenic driving forces. Meteorological drought is a major natural driving force of desertification and occurs due to the extended periods of low precipitation. Scarcity of water, as well as the excessive use of water resources, mainly for agriculture, creates negative water balances and changes in plant cover, and accelerates desertification. Despite various political measures having been taken in the past, desertification is still a serious environmental problem in many regions in Iran. In this study, drought and aridity indices derived from long-term temperature and precipitation data were used in order to show long-term drought occurrence in different climatic zones in Iran. The results indicated the occurrence of severe and extremely severe meteorological droughts in recent decades in the areas studied. Moreover, the De Martonne Aridity Index (I DM) and precipitation variability index (PVI) showed an ongoing negative trend on the basis of long-term data and the conducted regression analysis. Rapid population growth, soil salinization, and poor water resource management are also considered as the main anthropogenic drivers. The percentage of the rural population in Iran is decreasing and the urban area is growing fast. Since the 1970s, the usage of groundwater in Iran has increased around fourfold and the average annual decrease in the groundwater table has been around 0.51 m. The results of the study provide a better ex-post and ex-ante understanding of the occurrence of droughts as key driving forces of the desertification in Iran. Additionally, they can enable policymakers to prepare proper regional-based strategic planning in the future. Desertification cannot be stopped or managed completely, but could be mitigated by the adoption of some proposed sustainable land management strategies.
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hydrology
Article
Drought and Desertification in Iran
Iraj Emadodin *, Thorsten Reinsch and Friedhelm Taube
Institute for Crop Science and Plant Breeding, Group of Grass and Forage Science/Organic Agriculture,
Hermann-Rodewald-Straße 9, 24118 Kiel, Germany
*Correspondence: iemadodin@gfo.uni-kiel.de; Tel.: +49-431-880-1516
Received: 1 April 2019; Accepted: 5 August 2019; Published: 7 August 2019


Abstract:
Iran has dierent climatic and geographical zones (mountainous and desert areas),
mostly arid and semi-arid, which are suering from land degradation. Desertification as a land
degradation process in Iran is created by natural and anthropogenic driving forces. Meteorological
drought is a major natural driving force of desertification and occurs due to the extended periods
of low precipitation. Scarcity of water, as well as the excessive use of water resources, mainly for
agriculture, creates negative water balances and changes in plant cover, and accelerates desertification.
Despite various political measures having been taken in the past, desertification is still a serious
environmental problem in many regions in Iran. In this study, drought and aridity indices derived
from long-term temperature and precipitation data were used in order to show long-term drought
occurrence in dierent climatic zones in Iran. The results indicated the occurrence of severe and
extremely severe meteorological droughts in recent decades in the areas studied. Moreover, the De
Martonne Aridity Index (I
DM
) and precipitation variability index (PVI) showed an ongoing negative
trend on the basis of long-term data and the conducted regression analysis. Rapid population growth,
soil salinization, and poor water resource management are also considered as the main anthropogenic
drivers. The percentage of the rural population in Iran is decreasing and the urban area is growing
fast. Since the 1970s, the usage of groundwater in Iran has increased around fourfold and the average
annual decrease in the groundwater table has been around 0.51 m. The results of the study provide a
better ex-post and ex-ante understanding of the occurrence of droughts as key driving forces of the
desertification in Iran. Additionally, they can enable policymakers to prepare proper regional-based
strategic planning in the future. Desertification cannot be stopped or managed completely, but could
be mitigated by the adoption of some proposed sustainable land management strategies.
Keywords: desertification; aridification; drought; groundwater; water scarcity; salinization; Iran
1. Introduction
Desertification is a land degradation process that aects dryland areas. More than 250 million
people directly suer from the eects of desertification and more than 70% of drylands are currently
subject to desertification [
1
,
2
]. Moreover, approximately one billion people around the world are at
risk of the consequences of desertification [
3
]. Large areas of land in marginal areas of the world’s
deserts have been degraded and it is estimated that desertification is now taking place on around
12 million hectares per year [
4
]. Desertification results in a seriously undesirable situation for farmland
and settlement and it is a critical environmental threat worldwide e.g., [
5
7
], as well as for Iran [
8
].
In Iran, approximately 0.33 million km
2
(20% of Iran’s total land) is covered by desert [
8
,
9
] and around
one million km
2
of land is also at risk of desertification [
10
]. In the mid-1950s, projects to combat
desertification were established and since 1958, more than 2300 km
2
of sand dune areas have been
stabilized by oil mulch and about 21,000 km
2
has been improved through aorestation and sowing
programs [
11
,
12
]. Regardless of the many anti-desertification projects that have been implemented
Hydrology 2019,6, 66; doi:10.3390/hydrology6030066 www.mdpi.com/journal/hydrology
Hydrology 2019,6, 66 2 of 12
during the past six decades, desertification is still an important environmental issue in many parts of
the country and costs around one billion U.S. dollars annually [
3
,
13
]. Overgrazing, and the conversion
of rangelands into farmland and residential areas on the one hand, and poor irrigation practice on the
other, are the major anthropogenic driving forces of desertification in many parts of Iran [
9
], which are
accelerating the eects of natural driving forces such as climate variability and drought.
Desertification is strongly associated with drought. According to Mishra and Singh [
14
],
droughts and their eects are classified as meteorological, agricultural, hydrological, and socioeconomic.
Drought as a main driving force of desertification occurs due to the eects of extended periods of
low precipitation, so that its impact is mostly manifested as hydrological and agricultural droughts
following meteorological phenomena [
15
]. The main purpose of this study is to identify the spatial
and temporal variation of drought, as well as its specific eects in the context of Iran.
2. Materials and Methods
2.1. Study Area and Database
In terms of its physiography, Iran can be divided into four regions: Caspian, Central Plateau
(Kavir and Lut deserts), Zagros, and the Southern coastal plain [
16
]. Iran is located in the arid belt and
comprises around 1.6 million km
2
. More than 50 percent of the land area is mountainous and around
30 percent of the total land area (situated in the central plateau) receives low annual precipitation
(50–250 mm). Only the Caspian Plain in the north receives more than 1000 mm per year (Table 1).
The average annual potential evaporation is estimated to be more than 4000 mm in the central part
of Iran [17].
Monthly precipitation and temperature data used in this study were collected from 12 synoptic
stations distributed in Iran (Table 1; Figure 1) and were obtained from the Iranian Meteorological
Organization (https://irimo.ir/eng/index.php). Groundwater discharge data were obtained from the
Iranian Water Resource Management Company [18].
Table 1.
The De Martonne Aridity Index (I
DM
), annual precipitation, and mean temperature for the 12
synoptic stations over long periods.
Nr. Station Years Latitude
(N)
Longitude
(E)
Elevation
(m) a.s.l
Annual
Precipitation
(mm)
Annual Mean
Temperature
(C)
IDM Climate Type
1 Yazd 1951–2017 31540541701237 56.8 19.5 1.9 Arid
2 Zahedan 1951–2017 19280605301370 86.7 18.8 3 Arid
3 Iranshahr 1965–2017 2712060420591 108.2 27.6 2.9 Arid
4 Bushehr 1986–2017 28580504909 225 25 7.3 Arid
5 Mashhad 1951–2017 3616059380999 249.2 14.3 17.4 Semi-arid
6 Ahvaz 1957–2017 312004840022.5 328 14 13.7 Semi-arid
7 Shiraz 1951–2017 24320523601484 330.2 18.1 11.7 Semi-arid
8 Arak 1951–2017 34060494601708 328.5 13.9 13.7 Semi-arid
9 Orumiye 1951–2017 37400450301328 334 11.3 15.6 Semi-arid
10 Kermanshah 1951–2017 34210470901318.6 431.4 14.8 17.4 Semi-arid
11 Gorgan 1960–2017 36040542400 569 17.7 20.5 Mediterranean
12 Rasht 1956–2017 37190493708.6 1334.2 16.2 51 Very humid
Hydrology 2019,6, 66 3 of 12
Hydrology 2019, 6, x 3 of 13
Figure 1. Location of the synoptic stations which are considered in this study.
2.2. Drought Index
A large number of drought indices are used to monitor meteorological drought [19–22], but in
this study, the precipitation variability index (PVI) or standardized precipitation index is considered
because, according to Sivandi and Gharehdaghi [20], it provides more suitable results for Iran. The
precipitation variability index (PVI) was calculated based on the following formula to show a normal
distribution of the annual (twelve months) meteorological drought situation:
PVI
i
= (P
i
− µ)/ϭ (1)
where:
PVI
i
is the precipitation variability index for year i;
P
i
is the annual precipitation for year i; and
µ and ϭ are the mean annual precipitation in a selected period and standard deviation, respectively.
Precipitation time series are classified into different climatic regimes as follows [21,22]:
Extremely dry: P < µ − 2 × ϭ;
Dry: µ − 2 × ϭ < P < µ − ϭ;
Normal: µ – ϭ < P < µ + ϭ;
Wet: P > µ + ϭ
P is annual precipitation
A drought year is considered to occur if the PVI
i
is negative. Extremely severe drought occurs
when the PVI
i
is between −0.84 and −1.28 [20].
Figure 1. Location of the synoptic stations which are considered in this study.
2.2. Drought Index
A large number of drought indices are used to monitor meteorological drought [
19
22
], but in this
study, the precipitation variability index (PVI) or standardized precipitation index is considered because,
according to Sivandi and Gharehdaghi [
20
], it provides more suitable results for Iran. The precipitation
variability index (PVI) was calculated based on the following formula to show a normal distribution of
the annual (twelve months) meteorological drought situation:
PVIi=(Piµ)/σ(1)
where:
PVIiis the precipitation variability index for year i;
Piis the annual precipitation for year i; and
µand σare the mean annual precipitation in a selected period and standard deviation, respectively.
Precipitation time series are classified into dierent climatic regimes as follows [21,22]:
Extremely dry: P<µ2×σ;
Dry: µ2×σ<P<µσ;
Normal: µσ<P<µ+σ;
Wet: P>µ+σ
Pis annual precipitation
A drought year is considered to occur if the PVI
i
is negative. Extremely severe drought occurs
when the PVIiis between 0.84 and 1.28 [20].
Hydrology 2019,6, 66 4 of 12
2.3. Aridity Index
The de Martonne aridity index (I
DM
) is one of the best known and widely used aridity indices [
23
].
IDM was calculated based on the following equation [24]:
IDM =P/T+10 (2)
where:
P is the annual precipitation (mm) and
T is the annual mean air temperature (C).
The type of climate according to the de Martonne aridity index is shown in Table 2.
Linear regression is also used to compute the magnitude of trends.
Table 2. Type of climate according to the de Martonne aridity index (IDM).
Climate Type IDM Values
Arid IDM <10
Semi-arid 10 IDM <20
Mediterranean 20 IDM <24
Semi-humid 24IDM <28
Humid 28 IDM <35
Very humid 35 IDM <55
Extremely humid IDM >55
3. Results and Discussion
3.1. Drought
Drought is a complex natural event that has serious destructive consequences for agriculture,
industry, and the human environment. Droughts may be classified into four types: meteorological,
hydrological, agricultural, and socioeconomic [
25
]. The frequency and severity of drought in many
areas of the world are increasing due to the influences of natural and anthropogenic climate changes
e.g., [
26
,
27
]. Drought is a major natural driving force of desertification in Iran. The multi-decadal
average annual precipitation in Iran is 247 mm. There is also high spatial variability in the rainfall
distribution: approximately 70% of the total precipitation falls in only 40% of the area of the country.
According to Javari [
28
], a long-term analysis of annual precipitation in Iran shows significant variability
in the spatial and temporal distributions, as well as in the frequency and intensity.
The de Martonne Aridity Index (I
DM
), long term average annual precipitation, and mean
temperature for the 12 synoptic stations over long periods are presented in Table 1. The results show
considerable dierences in annual precipitation amounts between the recording stations. The regions
of highest precipitation are found in the Mediterranean and humid zones, as well as the mountainous
area in the west. The regions of lowest precipitation are located in the central plateau. In Yazd (centre),
Zahedan (east), and Iranshahr (south east), the annual precipitation levels are relatively low. However,
the annual precipitation in the other stations are all above 200 mm. Rasht located in the Caspian Plain
in the north receives around 1334 mm of precipitation per year on average. In contrast, Yazd in the
desert area receives approximately 57 mm of precipitation per year on average.
The long-term averages of the annual PVI values for each observed synoptic station are presented
in Figure 2. According to the classification of dierent climatic regimes, as mentioned above, evidence
shows that there have been severe meteorological droughts for all stations in recent decades. All the
recording stations experienced at least two main periods that were characterized by long and extremely
severe drought. In Kermanshah and Orumiye (west and north-west of the country), long periods of
Hydrology 2019,6, 66 5 of 12
severe droughts occurred during 1999–2017. The stations, which are located in the Central Plateau,
including Yazd and Shiraz, show extremely severe drought in the past decade. Moreover, the number
of extremely severe drought years at Yazd was higher than for the other stations. Gorgan synoptic
station, which is located in north Iran, and has a Mediterranean climate, also shows aridification
according to the de Martonne aridity index. Furthermore, an extremely severe drought condition was
indicated in 2008 and 2014 for this station. There was a severe drought in Zahedan station from 1999 to
2005 (Figure 2).
Hydrology 2019, 6, x 5 of 13
decades. All the recording stations experienced at least two main periods that were characterized by
long and extremely severe drought. In Kermanshah and Orumiye (west and north-west of the
country), long periods of severe droughts occurred during 1999–2017. The stations, which are located
in the Central Plateau, including Yazd and Shiraz, show extremely severe drought in the past decade.
Moreover, the number of extremely severe drought years at Yazd was higher than for the other
stations. Gorgan synoptic station, which is located in north Iran, and has a Mediterranean climate,
also shows aridification according to the de Martonne aridity index. Furthermore, an extremely
severe drought condition was indicated in 2008 and 2014 for this station. There was a severe drought
in Zahedan station from 1999 to 2005 (Figure 2).
Figure 2. Cont.
Hydrology 2019,6, 66 6 of 12
Hydrology 2019, 6, x 6 of 13
Figure 2. Annual precipitation variability indices (PVI) for the six selected synoptic stations from four
different climate types. The dashed red lines (right) show the five-year moving average. The solid red
lines (left and right) denote a simple regression analysis. Source: Iranian Meteorological Organization
(https://irimo.ir/eng/index.php).
The de Martonne Aridity Index (I
DM
) calculated for the recording stations shows a negative trend
(Figure 2). The spatial distribution of I
DM
shows a high variability, with the lowest values in Yazd for
the driest conditions in the center, and the highest values in the Caspian Plain in the north (Figure 2;
Table 1). I
DM
varied from 1.9 at the Yazd station to 20.5 and 51 at the Gorgan and Rasht stations,
respectively. The Yazd station is arid, while Goragn and Rasht stations are Mediterranean and very
humid. The reduction of I
DM
at the Yazd station was greater than for the other stations (Figure 2). This
negative trend could also indicate aridification in all study areas. The trend of the aridity index in
Mashhad station (north east of the country) shows the change of climate type from semi-arid to arid
(Table 2).
Table 2. Type of climate according to the de Martonne aridity index (I
DM
).
Climate type
I
DM
Values
Arid
I
DM
< 10
Semi-arid
10 ≤ I
DM
< 20
Mediterranean 20 ≤ I
DM
< 24
Semi-humid 24≤ I
DM
< 28
Humid 28 ≤ I
DM
< 35
Very humid 35 ≤ I
DM
< 55
Extremely humid I
DM
> 55
Drought has negative influences on agriculture. The central plateau, which is considered to be
the major area of the country, is characterized by having I
DM
values of 1.9 to 13.7. The main
agricultural activity in this area is the production of wheat, barley, cotton, and canola, which are all
at risk of water scarcity. Regarding the severe drought that has been shown in this study, high yields
cannot be achieved without using irrigation. Therefore, overexploitation of ground water will
Figure 2.
Annual precipitation variability indices (PVI) for the six selected synoptic stations from four
dierent climate types. The dashed red lines (
right
) show the five-year moving average. The solid red
lines (
left
and
right
) denote a simple regression analysis. Source: Iranian Meteorological Organization
(https://irimo.ir/eng/index.php).
The de Martonne Aridity Index (I
DM
) calculated for the recording stations shows a negative trend
(Figure 2). The spatial distribution of I
DM
shows a high variability, with the lowest values in Yazd for
the driest conditions in the center, and the highest values in the Caspian Plain in the north (Figure 2;
Table 1). I
DM
varied from 1.9 at the Yazd station to 20.5 and 51 at the Gorgan and Rasht stations,
respectively. The Yazd station is arid, while Goragn and Rasht stations are Mediterranean and very
humid. The reduction of I
DM
at the Yazd station was greater than for the other stations (Figure 2).
This negative trend could also indicate aridification in all study areas. The trend of the aridity index
in Mashhad station (north east of the country) shows the change of climate type from semi-arid to
arid (Table 2).
Drought has negative influences on agriculture. The central plateau, which is considered to be the
major area of the country, is characterized by having I
DM
values of 1.9 to 13.7. The main agricultural
activity in this area is the production of wheat, barley, cotton, and canola, which are all at risk of
water scarcity. Regarding the severe drought that has been shown in this study, high yields cannot
be achieved without using irrigation. Therefore, overexploitation of ground water will continue in
the future and will also accelerate the impacts of meteorological drought. Therefore, there is a need
to formulate eective water management for agriculture in this region. The results of this study
may therefore be useful in terms of raising awareness among decision makers in order to ensure the
better management of water resources in arid and semi-arid lands with regard to the prediction of
drought occurrence.
One of the main negative environmental impacts of drought is the reduction in groundwater
recharge due to the shortage of surface water. In addition, the overexploitation of water resources
by human activities leads to a severe water deficit and this has impacts on both natural vegetation
cover and the production of agriculture crops e.g., [
29
]. According to Linsley et al. [
30
], a hydrological
drought occurs when groundwater and surface water availability is not sucient to supply the demand.
Moreover, it should also be pointed out that dierent types of drought, including meteorological,
agricultural, and hydrological droughts, have significant eects on local economies and businesses,
and thereby cause socioeconomic drought [
25
,
31
]. According to Guo et al. [
25
], socioeconomic drought
Hydrology 2019,6, 66 7 of 12
will take place when the water supply cannot meet various human demands and related sectors.
Despite the importance of socioeconomic drought, it has generally received little attention [25,31].
3.2. Overexploitation of Groundwater
The water shortage worldwide is considered a key threat for the twenty-first century [
32
]. The issue
of water scarcity in Iran is long-term and it has become a chronic environmental problem. Iran has
been facing increasingly severe water scarcity, especially in recent decades, mainly in the central part
of the country. Inadequate precipitation is the main cause of water scarcity, but anthropogenic drivers,
such as rapid population growth and poor water resource management, also play an important role.
Approximately 89.5 billion cubic meters per year of fresh water are consumed by human activities
in Iran and around 93% of this amount is used for agricultural purposes [
33
]. Farmlands under
irrigation are estimated to comprise around 8 million hectares. Water use for irrigation is supplied
from both surface water and groundwater resources, in proportions of 45% and 55%, respectively.
Groundwater plays a very important role in Iran’s agricultural operations; every year, an average
of approximately 44 billion cubic meters of water is supplied for agricultural purposes from around
363,000 deep (>50 m) and semi-deep (<50 m) wells [
33
,
34
]. According to the Iranian Water Resource
Management Company [
18
], the exploitation of groundwater in Iran has increased from around
16,517 million cubic meters in 1972 to about 61,093 million cubic meters in 2014 due to increased
human consumption, land use change, and the irrigation of farmland, especially so following the rapid
population growth and urbanization that has occurred since 1975 (Figure 3). Therefore, the exploitation
usage of groundwater in Iran has been increased around fourfold and the average annual decrease
in the groundwater table has been around 0.51 m [
34
]. The mean yearly decrease in the level of the
groundwater table is around 50 cm in central Iran [
8
]. Therefore, pumping of the groundwater urgently
needs to be regulated.
Hydrology 2019, 6, x 8 of 13
Figure 3. The annual amounts of extracted ground water in Iran. Source: Iranian Water Resource
Management Company [18].
3.3. Salinization
Areas with saline soils are expanding in Iran and now cover 25% of the total area of the country
[35]. Salinization is an important factor of soil degradation in the central plateau of Iran and is also
considered a challenge in terms of land management activities [36]. High salinity can reduce the
conversion of ammonium salts to nitrate by soil organisms, thereby reducing soil fertility [5].
Farmlands in Iran are suffering from salinization as a result of anthropogenic activities and natural
processes [17]. Overexploitation of the groundwater from saline aquifers is considered to be an
important man-made driving force of salinity [37] (Table 3). Salinization effectively reduces the
capacity of groundwater-connected habitats [38] and hence, it reduces the productivity of land and
accelerates desertification. Around 50% of the irrigated lands in Iran are facing various rates of
salinity, which normally causes a loss of soil health and quality [39].
According to Qadir et al. [17], extreme saline soils are located in the Central part, Southern
Coastal Plains, and the Caspian Coastal Plain of Iran. The annual economic losses due to salinization
are estimated to be around US $1 billion for the whole country.
Table 3. Soil salinity level in irrigated lands in Iran.
Salinity Level Irrigated Land (million ha) dS/m
Slight 0.9 4–8
Moderate 1.2 8–16
Strong 1.5 16–32
Very strong
1.1
>32
Total 4.7
Source: Moameni [39].
3.4. Economic and Socio-Political Implications of Desertification
Desertification is not only an environmental problem, but it is also an important economic
problem that has direct impacts on incomes in rural areas [40]. According to Sivakumar and Stefanski
[41], the worldwide decrease in income related to desertification in farmland is calculated to be
around 42 billion US dollars annually. Population and economic growth as socio-political and
economic drivers are increasing pressure on natural ecosystems globally [35,42,43]. Urbanization and
Figure 3.
The annual amounts of extracted ground water in Iran. Source: Iranian Water Resource
Management Company [18].
3.3. Salinization
Areas with saline soils are expanding in Iran and now cover 25% of the total area of the
country [
35
]. Salinization is an important factor of soil degradation in the central plateau of Iran and
is also considered a challenge in terms of land management activities [
36
]. High salinity can reduce
the conversion of ammonium salts to nitrate by soil organisms, thereby reducing soil fertility [
5
].
Farmlands in Iran are suering from salinization as a result of anthropogenic activities and natural
processes [
17
]. Overexploitation of the groundwater from saline aquifers is considered to be an
Hydrology 2019,6, 66 8 of 12
important man-made driving force of salinity [
37
] (Table 3). Salinization eectively reduces the capacity
of groundwater-connected habitats [
38
] and hence, it reduces the productivity of land and accelerates
desertification. Around 50% of the irrigated lands in Iran are facing various rates of salinity, which
normally causes a loss of soil health and quality [39].
According to Qadir et al. [
17
], extreme saline soils are located in the Central part, Southern Coastal
Plains, and the Caspian Coastal Plain of Iran. The annual economic losses due to salinization are
estimated to be around US $1 billion for the whole country.
Table 3. Soil salinity level in irrigated lands in Iran.
Salinity Level Irrigated Land (million ha) dS/m
Slight 0.9 4–8
Moderate 1.2 8–16
Strong 1.5 16–32
Very strong 1.1 >32
Total 4.7
Source: Moameni [39].
3.4. Economic and Socio-Political Implications of Desertification
Desertification is not only an environmental problem, but it is also an important economic problem
that has direct impacts on incomes in rural areas [
40
]. According to Sivakumar and Stefanski [
41
],
the worldwide decrease in income related to desertification in farmland is calculated to be around
42 billion US dollars annually. Population and economic growth as socio-political and economic drivers
are increasing pressure on natural ecosystems globally [
35
,
42
,
43
]. Urbanization and urban-sprawl
directly or indirectly cause the main changes in environmental qualities and functions with great
pressure on natural resources [
5
]. Moreover, both impact climate dynamics and accelerate desertification
and aridification e.g., [
44
46
]. Therefore, anthropogenic climate change and environmental change
could also be considered as the major driving force of migration [47,48] (Figure 4).
Hydrology 2019, 6, x 9 of 13
urban-sprawl directly or indirectly cause the main changes in environmental qualities and functions
with great pressure on natural resources [5]. Moreover, both impact climate dynamics and accelerate
desertification and aridification e.g., [44–46]. Therefore, anthropogenic climate change and
environmental change could also be considered as the major driving force of migration [47,48] (Figure
4).
Figure 4. An abandoned village as a consequence of the long-term drought and water scarcity near
the city of Qom in Qom Province, north central Iran (Photo: Emadodin).
The total land area of Iran is 1.65 million km2 and the population is around 82 million. Population
growth and urbanization are the main driving forces of environmental stresses. Since the late 1950s,
there has been rapid population growth in Iran. Between 1956 and 2018, the population increased
from about 19 million to more than 82 million. The rural population, as a proportion of the total in
Iran, is decreasing and the size of the urban area shows growth over the past six decades e.g., [49,50]
(Figure 5). Around 21 million people (about 25.6% of the total population) live in rural areas and
approximately one-fourth are engaged in agriculture [34]. Economic progress and population growth
are the basic and primary driving forces of unsustainable land-use changes and overexploitation of
natural resources and subsequent desertification in Iran. As an example, since the 1950s, Iran’s
farmland has increased by more than five times and deforestation has also occurred at a significant
rate [51].
Figure 5. Iran’s population growth in urban and rural areas. Source: Statistical Centre of Iran [42].
Figure 4.
An abandoned village as a consequence of the long-term drought and water scarcity near the
city of Qom in Qom Province, north central Iran (Photo: Emadodin).
The total land area of Iran is 1.65 million km
2
and the population is around 82 million. Population
growth and urbanization are the main driving forces of environmental stresses. Since the late 1950s,
there has been rapid population growth in Iran. Between 1956 and 2018, the population increased
from about 19 million to more than 82 million. The rural population, as a proportion of the total in
Iran, is decreasing and the size of the urban area shows growth over the past six decades e.g., [
49
,
50
]
(Figure 5). Around 21 million people (about 25.6% of the total population) live in rural areas and
Hydrology 2019,6, 66 9 of 12
approximately one-fourth are engaged in agriculture [
34
]. Economic progress and population growth
are the basic and primary driving forces of unsustainable land-use changes and overexploitation of
natural resources and subsequent desertification in Iran. As an example, since the 1950s, Iran’s farmland
has increased by more than five times and deforestation has also occurred at a significant rate [51].
Hydrology 2019, 6, x 9 of 13
urban-sprawl directly or indirectly cause the main changes in environmental qualities and functions
with great pressure on natural resources [5]. Moreover, both impact climate dynamics and accelerate
desertification and aridification e.g., [44–46]. Therefore, anthropogenic climate change and
environmental change could also be considered as the major driving force of migration [47,48] (Figure
4).
Figure 4. An abandoned village as a consequence of the long-term drought and water scarcity near
the city of Qom in Qom Province, north central Iran (Photo: Emadodin).
The total land area of Iran is 1.65 million km2 and the population is around 82 million. Population
growth and urbanization are the main driving forces of environmental stresses. Since the late 1950s,
there has been rapid population growth in Iran. Between 1956 and 2018, the population increased
from about 19 million to more than 82 million. The rural population, as a proportion of the total in
Iran, is decreasing and the size of the urban area shows growth over the past six decades e.g., [49,50]
(Figure 5). Around 21 million people (about 25.6% of the total population) live in rural areas and
approximately one-fourth are engaged in agriculture [34]. Economic progress and population growth
are the basic and primary driving forces of unsustainable land-use changes and overexploitation of
natural resources and subsequent desertification in Iran. As an example, since the 1950s, Iran’s
farmland has increased by more than five times and deforestation has also occurred at a significant
rate [51].
Figure 5. Iran’s population growth in urban and rural areas. Source: Statistical Centre of Iran [42].
Figure 5. Iran’s population growth in urban and rural areas. Source: Statistical Centre of Iran [42].
Poverty is also an important and controversial implication of desertification. According to Cleaver
and Schreiber [
52
], poverty is a driving force of desertification and also contributes to its acceleration
through land-use intensification, thus creating more environmental problems, as well as greater poverty.
Poverty and its environmental impacts are unlikely to be mitigated in the dryland areas unless there
is a sustainable management of natural resources and notable investment in plant, soil, and water
conservation, as well as in training and education.
Rapid population growth and an unsuitable population distribution, the over use of land, and poor
water resource management are recognized as three major causes of water crisis in Iran [
53
] that are
exacerbating the eects of climate change, as well as droughts. Therefore, a good awareness of drought
is important in order to provide early warnings of the threats to environmental resources [54,55].
4. Conclusions
The main purpose of this study was to show the interactions between the annual aridity trends
and drought behavior in Iran over a long period, on the one hand, and the consequences for the
dimension of desertification of agricultural land, on the other hand. Therefore, monthly precipitation
and temperature data from 12 synoptic stations with dierent climatic conditions were analyzed.
The reduction of I
DM
during the selected period was greater at stations in arid areas than other stations.
This negative trend could also indicate aridification in these regions, especially in recent decades.
According to the main issues mentioned above, drought as a natural driving force plays an important
role in desertification in Iran, especially in arid and semi-arid areas. Evidence shows extreme natural
events such as droughts and floods that could be related to climate change in general and to local
climate perturbations. The use of the de Martonne aridity index to assess aridification confirms
that there has been a long-term increase in all selected synoptic stations, which is mainly due to the
increased annual temperature and shortage of precipitation. The long-term precipitation variability
index (PVI) also shows severe meteorological droughts for all stations in recent decades. The trend of
de Martonne Aridity Index (I
DM
) during selected periods indicated a negative trend for all selected
stations, especially in the central plateau with arid and semi-arid climate. This negative trend will
lead to increased aridity in the future and a worsening of its present extreme drought situation in arid
and semi-arid areas. The total use of groundwater has also increased around fourfold since 1970 and
this plays an important role as an anthropogenic driving force of desertification in Iran. The findings
of this study also show that the people in the Iranian Central Plateau are at greater risk of extreme
Hydrology 2019,6, 66 10 of 12
drought and desertification than those in other parts of the country. Therefore, it is assumed that an
increase in the duration and magnitude of droughts will result in increased migrations.
It should also be pointed out that desertification in Iran cannot be stopped or managed completely,
but it could be mitigated by sustainable land management strategies. This requires:
An ecological-economic approach as a basis for ensuring an integrated and coordinated approach
to find various policy alternatives;
A logical balance and management between the needs of society and the exploitation of
natural resources;
Participation of local non-governmental organizations in water-management decisions to achieve
sustainable watershed management;
Investigation of best water supply and storage methods and modified irrigation systems to
enhance the water use eciency;
Adaptive and proper management frameworks in rural development projects to provide an
appropriate basis for accelerating the process of combating desertification;
Multidisciplinary works to combine modern scientific findings with indigenous knowledge;
Assessing the opportunities that can be achieved through controlling desertification and land
restoration attempts as pilot projects through an optimal policy;
Improving information for decision-makers about environmental policy and their responsibilities
for the monitoring of environmental impacts.
Author Contributions:
Conceptualization, I.E.; methodology, I.E.; formal analysis, I.E., T.R.; investigation, I.E.,
T.R.; data curation and analysis, I.E.; writing—original draft preparation, I.E.; reviewing and editing, I.E., T.R. and
F.T.; funding acquisition, F.T.
Funding: This research received no external funding.
Acknowledgments:
The authors gratefully thank anonymous reviewers for their invaluable comments and
constructive suggestions.
Conflicts of Interest: The authors declare no conflicts of interest.
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article distributed under the terms and conditions of the Creative Commons Attribution
(CC BY) license (http://creativecommons.org/licenses/by/4.0/).
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