Benefits mainly come from economic usage which can be obtained from the statistics. Some benefits of the forestland come from ecological value (
Section 3.1.1) which includes water conservation (Equation (1)), water purification (Equation (2)), soil reinforcement (Equation (3)), carbon fixation (Equation (4)), oxygen release (Equation (5)), atmosphere purification (Equation (6)), crop/pasture increases due to forest protection (Equation (7)), protecting biodiversity (Equation (8)), and forest recreation income from visitors (Equation (9)). Benefits also come through social value (
Section 3.1.2), which includes income/value brought by forestland through scientific research (Equation (9)), employment (Equation (10)), health value (Equation (11)), and social development (Equation (12)).
3.1.1. Determining Ecological Benefit
(1) Water Conservation
The calculation reflects the relationship between water resource consumption and economic/social development due to systematic interactions between anthropogenic production, consumption activity, and water resources. The market value method is used in the study to evaluate the value of forest material production services. The market value method measures the economic benefits or losses of changes in environmental quality by using changes in regional output or profits caused by environmental quality changes [
18].
The value of the annual water content regulation of a forest stand (Yuan/yr) is:
where
Ck is unit volume income of the reservoir operation (Yuan·m
−3);
A is the area of the forest stand (ha);
P is precipitation (mm/yr);
E is evaporation of the forest stand (mm/yr); and
C is surface runoff (mm/yr).
For the water purification value, we used the method of price substitution of tap water, which means the value is calculated using the tap water price [
17]. The formula is:
where
K is the price of tap water (Yuan/t); and the other indicators are as above.
(2) Soil Reinforcement
Soil reinforcement and fertility maintenance are normally considered together [
19]. Soil reinforcement means reducing soil erosion. So we compare the non-forestland and forestland to calculate the net productivity of the forest soil in the research area. However, the income of fertility maintenance is always small, so we omitted fertility maintenance.
The value of soil reinforcement (Yuan/yr) is:
where
Cn is the output value of farmland (Yuan·m
−3);
Ct is the annual income after land development (Yuan·m
−3);
X2 is the soil erosion modulus of non-forest land (t·ha
−1·yr
−1);
X1 is the soil erosion modulus of forest land (t·ha
−1·yr
−1); and
ρ is the volume weight of soil (g·m
−3).
(3) Carbon Fixation and Oxygen Release
We calculated this measure by summing the incomes of carbon fixation and oxygen release [
20], then calculated the income of carbon fixation (Yuan/yr) as:
where
Cc is the market price of carbon dioxide (Yuan·yr
−1);
Rt is the carbon content of carbon dioxide with the percentage of 27.27%;
Bn is the net productivity of forest stand (t·ha
−1·yr
−1); and
Ft is the annual carbon fixation content of the soil of the forest stand (t·ha
−1·yr
−1).
The volume of oxygen release can be calculated by the carbon dioxide fixed by the forest. We choose a method called the shadow price method (SPM) to evaluate the oxygen’s market value. The oxygen price was taken to be the market price of oxygen for medical use [
21]. The equation for the value of oxygen release (Yuan/yr) is:
In this formula, Uo represents the annual oxygen release value of forest (Yuan·yr−1); Co is the market price of oxygen in 2011 (which was 1200 Yuan·t−1), and the other indicators are as above.
(4) Atmosphere Purification
This measure is based on the per unit area volume of pollutants and dust that are absorbed by forests and calculates the total pollutants and detained dusts assimilated by forests [
17]. The value is calculated by the method of market value. The annual air purification value of the forest (Yuan/yr) formula is:
where for each type
i of pollutant (SO
2, HF, NO
x) and detained dusts,
Ki represents the cost of air purification (Yuan·kg
−1); and
Qi is the volume of annual absorption (kg·ha
−1·yr
−1).
(5) Forest Protection
It is of interest to know how forest protection is related to issues of social and ecological justice, exploring whether forest exploitation based on the top-down managerial model fosters an inequitable distribution of resources [
22]. The value substitution method of disaster mitigation and yield increase is used to check the forest’s value in alleviating disaster and increasing production. The formula for the value of forest protection (Yuan/yr) is:
where
n represents the number of types of crop and pasture, and for each type, respectively,
Qi is the increased production of that type of crop/pasture due to protection by the forest (including coastal protection forest) (kg·ha
−1·yr
−1); and
Ci is the income from the type (Yuan·kg
−1).
(6) Biodiversity
The contingent value method (CVM) is usually used to evaluate the value of environments that have intangible benefits, and mainly uses a questionnaire survey to directly examine the economic behavior of respondents in a hypothetical market in order to obtain consumer willingness to pay for goods or services [
20]. In this study, the benefits of biodiversity can also be evaluated in this way, that is, by asking similar questions such as “How much are you willing to pay each year to preserve the living wildlife in per unit area?” The average of the answers is used to be an annual income opportunity. It is satisfactory as the price range to calculate the corresponding income per unit area. The income value (Yuan/yr) of protecting biodiversity is:
where
n is the number of species and for each species
i; and
Si is the annual income opportunity per unit area (Yuan·ha
−1·yr
−1). As before,
A is the area of forest stand.
(7) Forest Recreation
The research built a hypothetical market and obtained the WTP (willingness to pay) of the respondents [
21]. The annual value of forest recreation was evaluated by the question in the designed questionnaire: “In order to enjoy the natural scenery, how much are you willing to pay for this tour?” If the respondents gave a positive answer, the questionnaire will further inquire the maximum amount to be paid, reasons for payment, and ways of payment. In this study, the data sources of forest recreation services valuation were based on the random sampling principle. Questionnaires were used in the field survey. A total of 300 questionnaires were handed out and 287 questionnaires (95.67%) were actually recovered. Among them, 277 questionnaires were valid, giving a 96.51% effective recovery rate of questionnaires.
This paper follows the above opinions and adopted
WTP as the
CVM (contingent value method) research and evaluation indicators.
where
N represents the number of yearly tourists;
E(
WTP) represents per capita
WTP; and
TNUV represents non-use value.
E(
WTP) can be expressed using the following model [
23,
24]:
where
pi is the probability that the visitor will be willing to pay for Yanqing District and
Bi is the bid amount. The correlation between the
WTP obtained in the questionnaire and individual social characteristic variables meeting the principles of economics is one of the methods for determining the validity of CVM [
25].
3.1.2. Social Benefit
According to the structure of the research, the social income was divided into the income of scientific research, employment, health, and social development. The income earned from these services was considered to be only the economic benefits; we did not consider the economic value of the services when they entered the local or national market, so we used the benefit transfer method [
26].
The indicator is calculated by the total amount of scientific research funding as well as the transformation and income rate of such income. The formula is:
Here, Uk represents the annual income of forestry scientific research (Yuan·yr−1); N is the total amount of scientific research funds for forestry (Yuan·yr−1); m is the transformation rate of scientific research fruits of forestry (%); and n represents the social income rate of fruit transformation (%).
The specific calculation method of employment is to count the newly increased amount of employment in combination with the average wage. The formula is:
where
Ug represents the annual income of forestry employment (Yuan·yr
−1); ΔN is the newly increased employment population of forestry workers that year (people·yr
−1); and
w is the annual average wage (Yuan·yr
−1).
The main calculation method for health income is:
Here, Uh represents the annual income of human health (Yuan·yr−1); N is the number of local residents (people·yr−1); ΔY is the extended age limit of human life span (a); and G is the limit of willingness to pay (Yuan·yr−1).
The formula for social development income is:
where
Ud is the annual income of social development (Yuan·yr
−1); Δ
G is the annual average increase of GDP (Yuan·yr
−1); and
I is the influence coefficient of the existence of forest on GDP.