Prediction of the effects of global warming on biodiversity areas of Iran (Case study: the eastern part of mid-Zagros and the west of central desert of Iran)

Today, climate change is one of the most important scientific and even the political – social issues. The causes of climate change can be divided into natural and human‌-‌made. Natural factors have the long-term performance and long history, such as the cycle of solar activity, dusts and gases of volcanic eruptions, geodetic and static agents and etc. Human-made factors was mainly formed and accelerated in recent decades resulted from human activities such as industrial, agricultural, land-‌use changes, and in special emissions of greenhouse gases. Increasing trends in emissions resulted from various causes, especially due to the consumption of fossil fuels and industrial activities was very so fast that temperature changes in current decades is equal to resulted natural changes of mean temperature in many centuries. On the other hand increase of average global temperature will lead to changes in the amount, type and pattern of spatial and temporal distribution of precipitation. Changes in precipitation and temperature amounts in different geographical areas with different intensity as important inputs of systematic nature of environment, means that there is a period of rapid environmental changes, and therefore the severe consequences for human manipulation of the natural system will be expected. More governments and policy-makers interest to focuses on short-term phenomena and effects of climate change, for example drought, flood, frost and etc. But the long-term effects of climate change caused by slow mechanisms and are non-visible, less monitored by the governments. Climate is the most important factor in determining of plants distribution and their properties so that most of climatic divisions in the past has been based on the type of vegetation. Any changes in the components of the climate will affect the ecosystems, displacing the border of ecosystems and different biomes and will disrupt the existing environmental equilibriums. In this paper the impacts of global warming on biological zones in central parts of the Iran have been studied.
The study area consists of a limited corners between cities of Khoramabad (48°.17' East 33°.26' North), Kashan (51°.27' East 33°.59' North), Yazd (54°.17' East 31°.54' North) and Yasooj (51°.41' East 30°.50' North). This area was chosen due to the wide range of temperature and precipitation and also variety of biological zone in it.
Materials and Methods
   In this study, the Holdridge model was used to determine the areas of biological zone(Fig.‌1). By using three climatic parameters such as annual precipitation, annual ratio evapotranspiration and bio-temperature, Holdridge has prepared the biological zones in form of a chart. Base on Holdridge classification, the biological zones is divided into 16 areas of various zones. The bio-temperature is the measure of necessary heat which is utilized in the biological zones. The bio-temperature mean is an average with unit  of Celsius (C°) at which vegetations growth takes place in annual period. The range of temperatures within which vegetations growth occurs, is estimated to lie between 0° C as minimum and 30° C as a maximum. As far as possible, positive temperatures in the range must be averaged for the all years of period.
  A more accurate mean annual bio-temperature is obtained by adding up the daily bio-temperatues and dividing that sum by 365 or totals days of year. Also bio-temperature may be obtained by summing up the positive monthly temperature means and dividing by 12, the number of months in year. Evapotranspiration and annual precipitation form another sides of Holdridge's triangle of biological zones. Above  parameters have appropriate sufficient to determine of biological zones.
 
Fig(1): Diagram for the classification of world biological zones (Holdridge, L.R.,1984)
 
   In this study, we have used the 22 synoptic stations. Due to deficit of stations with sufficient data in the study area, the data of some neighboring stations has also been used.
  Two common scenarios A2 and B2, and four atmospheric general circulation models including UKHADCM3, ECHO-G, GISS-EH, and GFDLCM20 was used for temperature and precipitation prediction.  Scenario of A2 that focused on the local nature, leads to an increase in population. Thus, economic and technological development in this scenario is slower and more incomplete than other scenarios. As a result, this scenario predict the highest greenhouse gases emissions. Then, according to this scenario, the Earth's average temperature increase between 2.‌1° to 4.2‌° C until 2100. While the B2 scenario describes a world with greatest emphasis on local and regional strategies on sustainable economic, social and ecological issues. This scenario predicts a steady growth in population of the global and moderate economic development. According to this scenario, the Earth's average temperature increases by 2100 between 1.5‌° to 3.1‌° C. This four general circulation models of the most widely used for forecasting climate in Iran and other countries in many cases. In addition, the data that simulated by these models for observed data have shown better correlations than the other models.
  The model of MAGICC SCENGEN was used to prediction temperature and precipitation under global warming conditions. This model is a hybrid model and a model for the assessment of climate change caused by greenhouse gas emissions.  MAGICC SCENGEN is not a GCM model, this model combines the results of the scenarios of greenhouse gas emissions that defined in the MAGICC model and GCM results that defined in the SCENGEN model to assess the impact of these scenarios and models on different parts of the world. This hybrid model, including software that both SCENGEN and MAGICC models have been merged. The version of 5.3 this Model, include 49 variety emission scenarios, optimistic, pessimistic, moderate and their subdivisions and also include 20 general circulation model. According to the resolution 2.5×‌2.5 degree of this model, the study area is divided into six sub-zones and representative stations in each zone were determined and then above-mentioned scenarios and models were selected. Monthly temperature and annual rainfall of this zone for the years 2050, 2075 and 2100 was calculated. And these changes were applied to the stations that located in each zones.
Discussion of Results
  To determine the biological zones according to the Holdridge model, two climatic parameter of monthly bio-temperature and annual precipitation was used. Initially for these subject the holdridge method was used by using 22 synoptic stations mean monthly temperature for recent years (2000-1980) and future decades namely:‌ 2050, 2075 and 2100. Then by using of the IDW in geographical information system, GIS, zoning of bio-temperature and precipitation was done. By using GIS and two zoning of annual precipitation and bio-temperature and ranges that defined in the holdridge biological zones diagram,  biological zoning for study area was performed for the current period and then future period. According to holdridge zoning for the current period, from 16 various biological zone defined by holdridge, seven zones marked in study area. Eastern part of the study area covered by plains of central desert of Iran, but western edge of those plains, desertic conditions severely reduced and there is limited conditions for growth of plants and scrub and according holdridge classification is desert scrub biological zone. The severity of the dryness is extremely reduced in the Zagros Mountainous area. This situation has created by relative increase of precipitation and decrease of temperature, so that east part of the mid-highland of Zagros Mountains is marked by steppe and steppe woodland in holdridge classification. Because of the high frequency of precipitation in the most areas of Zagros Mountains, there are conditions for tree growth and to create of biological zones of wet forests and moist forests. The mean annual precipitation in the highlands of central Zagros Mountain is more than 1400 mm and under this this conditions moist forest biological zone was created. Despite, at lower altitudes annual bio-temperature is approximately equal to this height, because the average annual precipitation is less than 1000 mm, according to the holdridge classified are wet forests biological zone. The results showed that global warming reduce biological zones variety in this area at future  so that seven areas of biological zones in  today, will be reduce to six areas at future. Biological zones of moist forest and steppe will undergoes most effects by global warming. The whole of moist forest biological zone will be lost at future and wet and dry forests will occupied that area. Also the changes and shifts in the boundaries of biological zones will be significant by the effects of global warming.     
   Developing the desert and desert scrub biological zones to the west of study area is significant. So that the biological zone of desert that covers the areas of Yazd and Naain in the current period and only covers 1430 square kilometers of the study area  will have considerably extend to the west. All models show that the borders of the desert and desert scrub biological zones in 2100 will develop an average of 90 to 110 km toward the West. The GISS-EH model showed the most advance of this biological zone in the other models. While the model ECHO-G predict extending of desert and desert scrub less than other models. Also, according to This model, Influence of biological zones that located in the eastern half of central Zagros Mountains is less than the other models. Among this, the UKHADCM3 and GFDLCM20 models showed moderately affection of biological zones than the other two models.
   In all models, the shift in the biological zones boundaries by optimistic scenario; B2, less than A2 pessimistic scenario. The results of this study showed that the biological zones located in the Zagros Mountains would be affecte from global warming, so that steppe, dry forest, moist and wet forests will be subjected to reduction.
Conclusions
   More governments and policy-makers interest to focuses on short-term responses of climate change.  While the long-term impacts of climate change such as global warming is more important, for example the effects of global warming on the ecosystems, displacing the border of biological zones and biomes.
  The results of this research show that global warming reduce biological zones variety in study area. Biological zones of wet forest and steppe will encounter with serious impacts by global warming. The whole of moist forest will be lost at future and wet and dry forests put into area and dry forest will be replaced by parts of moist forests. Also this study showed that the biological zones that located in the Zagros Mountains suffered the great impacts from global warming and biological zones of this area, including steppe, dry forest, moist and wet forests will be reduced. extending the borders of desert and desert scrub zones to the west and eastern slopes of the Zagros Mountains will be significant.