Economic Valuation of Air and Noise Pollutions Abatement Performance

َAbstract
Green plans are among natural blessings which have many functions toward air quality improvement. On the one hand, plants moderate the air pollutants by photosynthesis; and on the other, beautify the cities. Many other functions have been found for the trees, of course, including the absorption of sound, water and soil pollutions. For this reason, in many nations, the creation of a green belt for inside and outside the cities has been set forth as a serious requirement but in the implementation of such projects, it is a must to select the species to be planted. The authors’ studies indicate that so far, no investigation has been done toward the selection of tree species across the city of Ahwaz [Iran]. This is a city with a hot, arid climate where the temperature rises to 57 degrees Celsius in the summer; and suffers from many environmental problems such as particulates and industrial pollutions. But the landscape planners in the city of Ahwaz are confused and occasionally, the expenses for planting trees are made with little efficiency. The selection of the best air pollution-reducing tree species may help policy makers toward optimal allocation of their limited resources. On the other hand, the budget allocated to the Organization for Landscapes and Parks of Ahwaz City Hall is not proportional to the economic benefits of the real interests of urban landscape. Achieving economic benefits of the best pollution-absorbing tree species may be used as a scientific criterion for optimal allocation of funds to this organization. Also, using the results of this study, the citizens’ awareness of the importance of trees is improved which could result in a more friendly treatment of landscape on their part and prevent the cutting of trees for banal reasons.
So far, many studies have been performed in various nations toward valuation and appreciation of natural and environmental resources such as parks, forests, lagoons, etc. (Juutien et al., 2011; Jenkins et al., 2010; Westerberg et al., 2010; Setlhogile et al., 2011; Cui et al., 2012; Newell and Swallow, 2013). However, to the authors’ experience, no studies have been done so far appreciating a tree species which might have the most attractive ability in absorbing air pollutants concerning the city of Ahwaz. Additionally, in most studies, the figures obtained for the tendency toward final payment have not been generalized to the overall community benefitting from the advantages; and therefore, the value of natural resources have not been calculated as a natural capital. Moreover, the contribution of natural resource functions value in the provincial, regional, or national gross production has not been considered; which is a very important factor in funds allocation and also in the movement toward national green accounting and environmental evaluation of projects.


2. Materials and Methods
The methods applied in this study is the choice modeling method, which assumes the individuals to have a rational behavior so that by choice, they would maximize their desirability considering the budget constraint. Therefore, it is assumed that any respondent has a random desirability function (Ben-Akiva, 1985). A random desirability function consists of a specific, observable component and a random one (Montazer-hojjat and Mansoori, 2016). A random parameter logit model would be suitable to explain such conditions:
Where um is the desirability of the nth individual, a binary variable; P, the protection cost for tree species or their improvement across the city; Ai, selected quality features of the tree such as air and sound pollution absorption, providing a delightful natural landscape, and educational services; Aisocij, an action variable of socio-economic characteristics of respondents and quality features of the intended tree species. Obviously, the socioeconomic characteristics of individuals are fixed at the time of their selection among the options and therefore, they appear in the model in action form with the features of tree species. After estimating the above model, the tendency toward final payment is obtained through dividing the estimated coefficient for each feature (i) by the estimated price coefficient (1):
However, an important stage of this study has been the selection method for the best air-and-sound pollution-absorbent tree species as well as the field survey method applied in this section. For this purpose, three species with the highest frequency across the city of Ahwaz, Concarpus Erectus, Albiza Lebbeck, and Eucalyptus Globulus, were selected based on the data provided by the Parks and Landscapes Organization. To select the superior species in terms of air and sound pollution absorption, the Air Pollution Tolerance Index (APTI) was applied. This index is calculated using four parameters, namely, total chlorophyll, leaf extract pH, relative water content, and acid ascorbic concentration) (Pathak et al., 2011). To perform laboratory process and calculate the APTI, the sampling process from the leaves of selected trees was performed in five highly trafficked areas, namely, north (Kianpars), south (Golestan), east (Zeytoon Kargari), west (Kamploo), and downtown Ahwaz (Amaniyeh), randomly.
Leaves from three selected species were collected in three different time frames during June 2015; and for each species in each area, three plants were sampled randomly as replicas. Coevality of the trees, given the commensuteness in diameter and length of their trunks was also taken into account. Leaves collected in frozen environment (zero degrees Celsius) were directly transported to the laboratory.
Later, relative moisture and pH of leaf extract were measured. In order to measure other parameters, collected leaves were stored in zero degree Celsius conditions so that their properties would not change. Ultimately, the figures obtained from the experiments were fed into SPSS21 software for analysis.
3. Discussion of Results and Conclusion
The results obtained from the measurement of five parameters, i.e. pH, RWC, ASC, CHL, and APTI, for three selected tree species, led to the selection of Albiza Lebbeck as the superior species in terms of air and sound pollution tolerance/absorption. The benefits of this species were also calculated for city residents. Tendency to final payment for four functions of this species was obtained dividing estimated coefficient for each feature by the price coefficient. They include tendency to final payment for natural landscape (Rials 1,418,128.4); reduced air pollution (Rials 1,692,708.9); reduced sound pollution (Rials 1,770,981); and educational performance (Rials 1,653,938.4). Additionally, the annual value of benefits and capital value of this species were calculated to be Rials 1,167 and 1,852 B, respectively.
Using the figures obtained for annual value of social benefits of Albiza Lebbbeck species, the municipality of Ahwaz will be able to direct the budget of the Parks and Landscapes Organization toward higher efficiency; and to determine its budget based on every citizen’s landscape quota and the figures obtained by this study. Additionally, the municipality may use those numbers to determine the tendency of residents to pay renovation and building license charges; and to update previous numbers.
Given the results of this study and the enormous capability of Albiza Lebbeck in absorbing and metabolizing the pollutants, it is recommended that planting this species be included in agenda in highly trafficked areas of the city of Ahwaz such as the downtown, along city roads, industrial zones, factories, and other areas where there is a possibility of air pollution. Also, by using the results of this study and the obtained figures, it is possible to improve social awareness on real value of this species’ functions, enhancing their sense of responsibility to protect it, and to prevent their unnecessary cutting. Also, the results of this study can be used as a basis to fine the breaching citizens for cutting the trees. Another use for the results of this study is in the field of economic-environmental evaluation of urban projects. The figures obtained by this study can be used to evaluate the projects which might require cutting the trees. Thereby, environmental costs will be included in calculations; and the justification for some projects might even be questioned.