In developing countries, dam construction has always been considered as an engineering method for supplying irrigation water in farms, storing drinking water, energy production, flood control and other applications (Ayeni and Ojifo 2018; Heydari et al. 2013; McCartney 2009; Sönmez and Kılıç 2014; Zare and Kalantari 2018; Divine et al. 2017; Qicai 2011; Caspary 2009; Yang et al. 2019). Dam construction has a historical background in Iran, with its dry and semi-arid climate, especially in order to prevent water wastage, deal with water shortage crisis, and regulate river water flow (Tajziehchi et al. 2012). There are different views on the dam construction in the world, which have their own pros and cons among the experts.
Although dam construction has many benefits for human beings, it has also causes damages that have been irreparable in some cases, because in most cases and in practice, dam construction does not take into account environmental considerations or the necessary forecasts to reduce the environmental, economic and social harms (Brown et al. 2009; Beck et al. 2012; Divine et a. 2017; McCartney 2009; Paul et al. 2013; Biswas and Tortajada 2001; Wiejaczka et al. 2020). This has come to a point that some international organizations have conducted studies and proposals to stop the dam constructions, especially in developing countries (Caspary 2009; World Commission on Dams 2000).
Among the effects of dam construction, mentioned in many studies, their effects on the energy and hydrological cycles of the region, changes in river flow, changes in hydrological and geomorphological system of the region, changes in frequency, peak and duration of floods in the region, reduction of river water flow and changing in the riverbed, increased evaporation from the dam water level that causes changes in the chemical properties of water, increased environmental pollution, spread of waterborne diseases, forced migration of residents of surrounding villages, changes in land use from rangeland and forest lands to agricultural lands and factories, disconnection of path roads from existing roads, reduction of land fertility, increased soil salinity, negative effects especially on the survival of riparian ecosystems, biomass production and survival of plant ecosystems adjacent to the dam, reduction of water table levels in the downstream areas of the dam, drowning or threatening historical monuments and cultural heritage, and so on (McCartney 2009; Heydari et al. 2013; Sönmez and Kılıç 2014; Ayeni and Ojifo 2018; Brown et al. 2009; Qicai 2011; Paul et al. 2013; Caspary 2009; Wiejaczka et al. 2020). On the other hand, the existence of dam resources increases the possibility of developing new water uses such as fish farming, fishing and tourism and creates more opportunities for the development of aquaculture with its effects on the local climate. Also, the effect of climate change and increased air humidity due to dams causes higher yield of dryland farming (Moradi et al. 2010).
Dam construction, like other forms of industrial development, has short-term and long-term positive and negative effects on natural ecosystems around the project areas (Zare and Kalantari 2018; Tajziehchi et al. 2012; Divine et al. 2017; McCartney 2009). But perhaps the most important effects of building large dams are their adverse effects on the region's natural ecosystems, including the destruction of forests in the dam reservoir, habitat fragmentation, food chain breakage, and increased pressure on forest resources around the dam (Ayeni and Ojifo 2018; Brown et al. 2009; Tajziehchi et al. 2012; Vale et al. 2015; Chen et al. 2015; Paul et al. 2013; Caspary 2009).
Additionally, there is no doubt that the presence of vegetation on the surface of the basin is one of the factors that reduce flooding due to the effects it has on the components of the hydrological cycle (Rezaian et al. 2016; Yang et al. 2019). Therefore, the conservation, restoration and creation of vegetation are very important due to their great impacts on increasing the permeability and duration of concentration and control of surface runoff and other services. Deforestation and destruction of vegetation around dams will reduce the penetrability of the soil or increase the drainage capacity of the basin, which in turn will lead to an increase in flood discharge (Qicai 2011; Chen et al. 2015). Therefore, the environmental impact assessment of dam construction should be considered in a comprehensive manner.
In developing countries, it is usually assumed that the economic benefits of building dams outweigh its costs, thus providing a logical reason for building dams. But this should not be taken as a loophole to ignore its social and cultural, and especially ecological, damages (Beck et al. 2012; Biswas and Tortajada 2001; Wiejaczka et al. 2020). Although in most parts of Iran, dam construction may be economical in some respects, it is not compatible with the sustainable and comprehensive development plan (Moradi et al. 2010; Zare and Kalantari 2018). In the triangle of sustainable development, striking a balance among economic, social and environmental components at any time and place requires spending money obtained from other sectors in the less developed sector. On the other hand, the emphasis is on meeting the needs of the current and future generations. Therefore, the only way to achieve sustainable development is to pay enough attention to all the ecosystems downstream and upstream of the dams (Heydari et al. 2013; McCartney 2009).
Dam construction causes damage to the natural ecosystems and it is not possible to compensate for the damages, but its damages can be reduced (Moradi et al. 2010). When the decision is made on the construction of the dam, an attempt should be made to adopt a policy that minimizes the threat. A wide range of technical and non-technical operations have been proposed to improve the negative effects of dams (McCartney 2009). Given the inevitable damages from dam construction on the surrounding natural resources, especially forests, methods that can provide solutions to reduce or compensate for the damage in the form of applied policies, can be useful to take utmost care and adopt the right policy in order to refrain from any unconsidered actions (Moradi et al. 2010; Loncar et al. 2006).
Forests are among the natural ecosystems threatened by dam reservoirs. Forest ecosystems have undeniable advantages that are of great interest to policymakers, and in many cases the advantages have not been valuated or are difficult to measure (Jahanifar et al. 2017; Musi et al. 2017; Amirnejad et al. 2006). With the construction of dams, many of these services provided by the forest ecosystem will be destroyed or the composition and biodiversity of forest communities will be changed (Vale et al. 2015; Chen et al. 2015; Beck et al. 2012). Numerous studies have been conducted on the valuation of forest resources (Amirnejad et al. 2006; Jahanifar et al. 2017; Ninan and Inoue 2013; Xue and Tisdell 2001). It is important to note that the numerical calculation of these values does not mean that these values are tradable, but is only a good way for calculating the compensation for damages (Amirnejad et al. 2006; Ninan and Inoue 2013).
Dam construction and the resulting consequences on forest resources is a complex phenomenon with different aspects, including various stakeholders, many components and parameters involved, and various goals. It includes a variety of ecological, economic, and social variables that have interrelated, complex relationships and interdependencies between their components. Today, the description of interrelations and the evaluation of their effects, especially the environmental and social effects of dam development, has become an important issue that plays a role in the sustainable development of communities and natural resources. Therefore, its inclusion in a systematic and integrated approach to a project based on sustainable development is important (Tundisi et al. 2015).
Based on the systems perspective, the dynamic system approach first developed by Forrester (1961) is an idea developed by system modeling methods (Forrester 1961). It consists of a series of cause and effect links through which the interaction between the elements of the system is shown (Olabisi 2010; Collins et al. 2013; Purnomo and Mendoza 2011; Hossain et al. 2020). This technique is used as a tool in the analysis and modeling of systems with various aspects, complex, reciprocal and nonlinear relations, and with feedback and delays (Tao et al. 2017; Machado et al. 2015). This model has been used in an interesting way in various scientific researches to model complex and dynamic natural and social systems such as natural resource system and forest, whose patterns are a function of time and need long-term planning (Collins et al. 2013; Hossain et al. 2020; Purnomo and Mendoza 2011; Olabisi 2010). The dynamic system method provides a demonstrative framework of the forest's natural environment, which responds to direct and indirect interferences, and its natural and unnatural disturbances (Blanco et al. 2017; Machado et al. 2015; Tao et al. 2017).
The power of simplification of complex natural phenomena such as problems of natural resources with different types of interconnected variables and having internal interrelationships, high speed and flexibility of the model in providing results, the ability to clarify interrelations, interactions and especially feedbacks, success in illustrating future changes and developments based on recognizing the structures and relations of variables in the past and present, are the special features of this model that prove its potential to solve management problems, especially in natural resource areas that we face, thus making it attractive for researchers to be used in studies (Olabisi 2010; Collins et al. 2013; Loncar et al. 2006; Tao et al. 2017; Sterman 2000; Musi et al. 2017). In fact, the purpose of systemic thinking and modeling using the dynamic system is to identify the causes, structures and relationships that have led to past changes and developments, in order to lead the developments and policies in the favorable direction (Collins et al. 2013; Musi et al. 2017; Sterman 2000; Olabisi 2010; Tao et al. 2017; Loncar et al. 2006).
The performance of the dynamics and scenario modeling system and the formulation of management policies and strategies in the forest based on its simulations has been tested in a series of studies with different criteria. In the oldest study, a dynamic system was used to simulate the dynamics of forest development (Bossel 1994). Also, modeling the dynamic system has been performed for forest fire management (Collins et al. 2013), planning for forest management (Loncar et al. 2006), simulating the dynamics of socio-ecological systems of forestry in adapting to climate change (Blanco et al. 2017), evaluating forest ecosystems (Tao et al. 2017), evaluating forest participatory management (Purnomo and Mendoza 2011), monitoring and evaluating forest growth and amount of carbon deposits (Machado et al. 2015), planting and reforestation planning in destroyed forest lands (Musi et al. 2017), and comparisons of forest management perspectives (Olabisi 2010).
The construction of Liro Dam in the Zagros Mountains, dominated by the ecosystem of unique forests of the Iranian Oak, is under consideration. Damage to the vegetative coverage of the dam will cause a lot of damage to the region's ecosystem if it is not compensated. In this study, the method of determining the amount of damage and the methods of restoration and reducing damage to the vegetation caused by dam construction in the region have been discussed. To conduct this study, first a dynamic system model was prepared for Oak forests in the region. Then, the value of ecosystem services of the existing vegetation and its changes over time was estimated in the dynamic system model. In the next step, different options for reducing damage and restoring vegetation under different scenarios and their impacts on damage compensation are examined. In the end, the optimal policies were introduced based on the best scenarios. The results of this study have the potential to provide solutions to reduce the adverse environmental impacts of dam construction by planning to restore the vegetation in the area and to prevent the continuation of forest degradation along the dam.