The areas that have been introduced in the field visit as areas susceptible to biological restoration mainly include areas with a slope close to zero, coastal estuaries and tidal areas with an average depth of one meter in full mode. Based on this, most of the areas prone to reforestation had optimum growth and survival rate more than 90 percent. Furthermore, all reforested trees started propagule production after age four. The stabilization of the forest was observed in all places after the fourth year, which can be mentioned in the indicators of reproduction, growth of new seedlings and survival of the wetland. In general, mangrove ecosystems are very vulnerable to various types of environmental disturbances and stresses.. They are plants that are sensitive to the formation of sludge, heavy sedimentation, waterlogging, waterlogging of surface water, and most importantly, oil and industrial pollution. These activities reduce the absorption of oxygen through respiration and increase the mortality rate of mangroves. Salinity above 90 ppt as a result of reducing the flow of fresh water and changing water level patterns due to the construction of dams, dredging, etc. causes the destruction of mangroves.
The most important natural factors affecting the development of mangrove forests are tidal regime, fresh water sources, bed type, drainage, water salinity, land slope, land use, climate, latitude, soil texture, humidity soil, the concentration of organic and mineral substances and the electrical conductivity of the soil (Safiari 2017). Three criteria and nine sub-criteria for the process of locating mangrove forest development areas and the identified criteria and sub-criteria using the Delphi method after screening including physical properties of the bed, chemical properties of the bed, tides, air temperature, water quality, climate type and rainfall as important criteria in locating have been introduced (Andon Petrosian et al. 2013).
In land identification, the most important factors affecting the growth and development of mangrove forests in the Qeshm Island, The Persian Gulf, Iran are tidal factors, soil saturation percentage, soil electrical conductivity, pH and soil texture, magnesium, sodium, sodium absorption ratio and the amount of soil sodium exchange (Dehghani et al. 2010). The shape and characteristics of the beach, water salinity and tides as conditions and factors affecting the distribution and establishment of mangroves are also introduced (Nagelkerken et al. 2008). Moreover, longitude and latitude, air humidity and temperature, tides, easy access to permanent fresh water, soil type (soil texture and its constituent elements, salinity and acidity) are the other factors affecting the formation of mangroves (Kamali and Hashim 2011). A map of suitable lands for planting mangrove species was prepared considering the criteria of soil texture, acidity, salinity, tidal area and land use pattern and weighting each criterion (Hossain et al. 2003).
In the land rehabilitation guide for mangrove cultivation that soil parameters including texture, density, percentage of rock formation, pH, electrical conductivity, amount of iron sulfide, amount of organic matter and mineral nutrients, ratio of carbon to nitrogen and soil moisture are very important in the successful establishment of this species in an area (Friess 2017). Reviewing the benefits of using low-cost principles in the re-establishment of mangrove forests in America showed that the important determining factors in the successful re-establishment and introduction of mangrove species in an area include the frequency and depth of inundation, wave energy, salinity and water and soil pH, soil type and texture, soil nutrients and slope (Gilman and Ellison 2007). Investigating the habitat of mangrove species in the coasts of India showed that while pointing out the importance of the elements in the soil in the success of planting mangrove trees, the salinity parameters, the pH of water and soil and soil texture are the most important parameters affecting mangrove communities (which have a large percentage of mangrove species) (Bhalla et al. 2008).
Regulating parameters (soil and water salinity, sulfide level and pH), resource parameters (soil nutrients, light and space) and periodic parameters of water (the duration, abundance and depth of waterlogging) are the most important parameters in the establishment of mangrove species (Berger et al. 2008). Regarding mangrove planting in order to rehabilitate saline and saturated agricultural lands, physical and chemical parameters of water and soil including pH, electrical conductivity, total dissolved solids, dissolved oxygen and salinity percentage in natural mangrove habitat in Pakistan have been considered. (Nazim et al. 2010). Despite the difference in water and soil characteristics, there is no significant difference in vegetation parameters in the two environments and in areas with high salt, saturated with water and unbearable for other species, mangrove is one of the few species that survives (Nazim et al. 2010).
The breakwater installation in an area with an almost regular tidal regime and with a maximum span of 2.3 meters, a gentle slope of 1% and in direct contact with waves with a height of less than one meter has led to the re-establishment of mangrove forests with a high percentage of mangrove species (Kamali and Hashim 2011). The temperature factor as one of the factors that affect mangroves in nature showed that mangroves face with a temperature of less than 15 degrees Celsius through the decrease in the rate of photosynthesis and the decrease in seedling growth indicated sensitivity (Simard et al. 2019). The results showed that the best conditions for the establishment of this species are in the range of water pH between 0.9 and 3. 8, the pH range of the soil is between 7.4 and 8.5 and the water salinity range is between 24 and 35 grams per liter and the type of soil is sandy loam, loamy clay (Bhalla et al. 2008). Mangroves become more dense under low salinity conditions and settle at salinities between 5 and 30 ppt (Joshi and Ghose 2003). Mangroves spend more energy to maintain water and proper ion concentration at high salinity conditions, so less energy is left for growth and primary production (Joshi and Ghose 2003). Also, high salinity reduces the leaf surface, increases the osmotic pressure of plant sap, increases the ratio of surface area to leaf weight, and decreases the amount of potassium, nitrogen, and phosphorus (Gilman and Ellison 2007). For maximum growth of mangrove species, the maximum is 50% (Safiari 2017).
The most important reason for the increase in the size of unsuitable areas for the growth and creation of mangrove forests in the areas planted in this study can be seen as the increase in construction, including the construction of roads, closing the entrances of fresh water, and closing the estuaries by increasing the area of shrimp breeding ponds or related channels with them, the construction of wharves and its destructive effects such as sedimentation or dredging, the destruction of the tidal zone by creating walls in these areas. The development of industries without taking into account the characteristics of the mangrove wetland ecosystem can cause the lack of flooding and the formation of a complete lagoon and increase of soil salinity, which can be considered as a limiting factor in establishment and planting of mangroves.
The benefits of rehabilitating mangrove wetlands in these places include increasing shelter for migratory birds, preventing of erosion of estuaries in tides and sea storms, increasing local fishing due to the increase in food for fish species with the expansion of wetlands, increasing tourist visits pointing out the places to plant mangrove trees, preventing the expansion of future industries due to the existence of laws restricting the presence of forest and also creating local and rural jobs for the residents around the wetland, from the production of saplings to the protection of the wetland. The services provided by mangrove forests are of significant importance to coastal communities and contribute to the sustainability and resilience of local economies (Hussain and Badola 2010). The costs and benefits of mangrove expansion with those created by aquaculture and forestry can achieve the goals of sustainability and equity as well as economic efficiency in coastal communities (Ron and Padilla 1999).