Strategies for Prioritizing Ecological Construction with Consideration of Agricultural Industry Development in Northern China’s Agro-pastoral Ecotone: A Perspective of Opportunity Cost

Liang REN, Fang SUN, Ding DING

1. Ecological Construction and Industry Development Research Center, Hebei North University, Zhangjiakou 075000, China; 2. College of Economics and Management, Hebei North University, Zhangjiakou 075000, China; 3. Office of Academic Affairs, Hebei North University, Zhangjiakou 075000, China

Abstract In northern China’s agro-pastoral ecotone, there are conflicts between agricultural industry and ecological construction resource competition, and also problems urgently to be solved for economic growth and sustainable ecological improvement. Taking the development concept of "lucid waters and lush mountains being mountains of gold and silver" as the guiding principle of prioritizing ecological and green development, this paper studied the strategies for prioritizing ecological construction with consideration of economic development of agricultural industry from the perspective of opportunity cost. Through the analysis of opportunity cost, externality, and Pareto optimal theory, and using the calculation method of the unit equivalent factor value of terrestrial ecological service function, this paper calculated the ecological service value of forest, grassland, and farmland. It found that the ecological value of forest and grassland per unit area was greater than the ecological value of agricultural industry. This indicates that the opportunity cost of farmland for ecological construction was less than that of agricultural industry. Based on the theoretical and quantitative analysis, it came up with recommendations for establishing a comprehensive system for prioritizing ecological construction with consideration of agricultural industry development and establishing and improving the incentive mechanism of ecological construction.

Key words Opportunity cost, Northern China’s agro-pastoral ecotone, Agricultural industry, Ecological construction, Coordinated development

1 Introduction

From the perspective of land use characteristics and agricultural zoning, the agro-pastoral ecotone has staggered distribution of farmland and grassland, and is a special ecological-economic-social complex ecosystem formed by the intervention and influence of human long-term agricultural activities, with coexistence of planting and grassland animal husbandry. In China, there are northern agro-pastoral ecotone and southern agro-pastoral ecotone. The northern agro-pastoral ecotone is located in the semi-agricultural and semi-pastoral area bordering the semi-humid agricultural area and semi-arid pastoral area. The northern agro-pastoral ecotone is characterized by staggered distribution of farmland and grassland, equal status of agriculture and animal husbandry, and has advantages of the development of herbivorous animal husbandry. However, its ecological environment is fragile and the economy is underdeveloped. In this region, there are conflicts between agricultural industry and ecological construction resource competition, and also problems urgently to be solved for economic growth and sustainable ecological improvement. Due to the impact of climate change and human activities, the boundaries of the northern agro-pastoral ecotone are constantly changing. As a strong influence area of human activities and a sensitive area of ecological environment, the northern agro-pastoral ecotone is a "hot spot" region for land use change research, and also an important ecological barrier in eastern and central China. In this ecotone, the herbivorous animal husbandry has efficiency advantages, scale advantages, and comprehensive comparative advantages. Nevertheless, the northern agro-pastoral ecotone has large wind erosion and desertification area of soil, the utilization efficiency of farmland natural resources is low, climate change has a huge impact on agricultural production, and food security is under threat. Since the northern agro-pastoral ecotone is a key area of China’s ecological civilization construction, it is necessary to attach great importance to the mitigation and adaptation of climate change in this region, to promote its sustainable development. To realize the real sustainable development of the region, we should pay attention to the fairness of income distribution and narrow the gap between the rich and the poor. Besides, it is necessary to select a proper spatial scale for the balance of ecosystem services to facilitate ecosystem management decision-making. In the coordinated development of ecological construction and industrial economy, it is necessary to continue to strengthen the promotion of ecological construction projects, expand the industrial operation scale, increase investment in ecological construction and industrial development, implement resource-saving production innovation models, and improve the ecological and economic coordinated development system. In recent years, the number of provinces staying in the coordinated stage of the coordinated development of ecological civilization construction and industrial upgrading is increasing. Based on its natural resource endowment, agricultural industry foundation, regional policy orientation, market demand and development direction, this region should build an eco-agriculture model integrating agriculture, animal husbandry and forestry, and a circular agriculture model within the environmental carrying capacity, and leisure agriculture model managed by manual intervention. Zhangjiankou City, as one of the 25 counties and cities in the Beijing-Tianjin-Hebei Water Conservation Area, one of the three major regions in the northern agro-pastoral ecotone, and the construction area of "two districts of the capital", is not only an ecological barrier for the Beijing-Tianjin-Hebei region, but also a connection to Shanxi and Inner Mongolia. It has outstanding geographical advantages. It not only connects the pure agricultural area, but also borders the pure pastoral area, and the characteristics of agriculture and animal husbandry are distinct. Some experts proposed to optimize the construction strategy of Beijing-Tianjin Water Conservation Functional Zone. This region should build an ecological environment management system and a green economy oriented ecological industry system, and improve an ecological compensation mechanism. Zhangjiakou City should follow the concept of Green Olympics, implement the strictest environmental governance, and take the "zero carbon" measures of ecological construction. As an agro-pastoral ecotone, the agricultural industry in this region should integrate the operation of agriculture and animal husbandry.

In 2005, General Secretary Xi Jinping stated that lucid waters and lush mountains are mountains of gold and silver (referred to as the concept of Two Mountains). Over a decade, the concept of Two Mountains has become the guiding principle of prioritizing ecological and green development. This concept is of great importance to prioritizing ecological construction with consideration of economic development of agricultural industry in northern agro-pastoral ecotone. The above findings provide precious experience for the study on strategies for prioritizing ecological construction with consideration of agricultural industry development in northern agro-pastoral ecotone. Under the above background, taking Zhangjiaokou City in northern agro-pastoral ecotone as an example, we studied the ecological construction and industrial development of the northern agro-pastoral ecotone. From the perspective of the opportunity cost theory, we compared the opportunity cost between agricultural industrial development and ecological construction of the study area, to provide theoretical and empirical basis for the coordinated development strategy of prioritizing ecological construction and industrial development. Our research perspectives, ideas, and theoretical basis have academic value, and research conclusions and recommendations are expected to provide references for the decision making.

2 Theoretical analysis

The northern agro-pastoral ecotone borders agricultural zone and is adjacent to the pastoral area, and also serves as the back garden of the capital Beijing. In the agricultural eco-economic system, the planting industry, the breeding industry and the ecological environment mutually promote and restrict each other. In them, there exists a complementary relationship of products and also a competitive relationship of resource utilization. Apart from meeting the basic consumer needs of human life, the agriculture and animal husbandry industries also have the characteristics of public goods and ecological functions.

2.1 Theoretical basis of ecology priority over industrial development

As early as in 2005, General Secretary Xi Jinping stated that lucid waters and lush mountains are mountains of gold and silver. In 2013, he stated that we want to have not only mountains of gold, but also mountains of green. If we must choose between the two, we would rather have the green than the gold. And in any case, green maintains are themselves gold mountains. These reflect the meaning of ecological priority, green development, and coordinated development of economy and ecology. Over a decade, the concept of Two Mountains has become the guiding principle of prioritizing ecological and industrial green development. The CPC Central Committee’s proposals for the formulation of the

14

Five-Year

Plan

(

2021-2025

)

for

National

Economic

and

Social

Development

and

the

Long-Range

Objectives

Through

the

Year

2035

clearly put forward major decisions and deployments to improve the quality and stability of the ecosystem. The priority of ecological development has become the most basic requirement of human sustainable development, pointing out the development direction for the northern agro-pastoral ecotone with high ecological fragility. In the end of 2016, the Ministry of Agriculture issued

Guiding

Opinions

on

the

Adjustment

of

Agricultural

Structure

in

the

Northern

Agro

-

pastoral

Ecotone

, clearly stating the range of this ecotone, that is 7 provinces, 25 cities and 146 counties (county-level cities), including 77 counties (county-level cities) in desertified degraded areas along the Great Wall, 44 counties (county-level cities) in loess hilly and gully regions, and 25 counties (county-level cities) in Beijing-Tianjin-Hebei water conservation area. According to this guiding opinion, the Northern Agro-pastoral Ecotone is the climatic intersection of semi-humid and semi-arid regions, it is a suitable development zone of grassland agriculture and farmland agriculture, an important ecological security barrier in the central and eastern regions, and also an important water conservation zone in the Beijing-Tianjin-Hebei region.

The characteristics of agricultural and animal husbandry operations in this ecotone are manifested in its resources and industrial characteristics. Its resource advantage is the staggered distribution of farmland and grassland; the agricultural industry advantage is the coexistence of planting and breeding. Planting and animal husbandry are roughly the same in the agricultural economy or planting is dominated, with a certain area of natural grassland and a certain scale of herbivorous livestock breeding. As stated by Xi Jinping, our mountains, rivers, forests, fields, lakes and grasslands together form a biotic community. humans need the fields for food, the fields need the rivers, the rivers need the mountains, the mountains need the soils, and the soils need the forests and grasslands. This biotic community is the material basis for humanity’s subsistence and development. A major goal of the structural adjustment of this region is to basically build an industrial system that integrates animal husbandry, agriculture, forestry, grass-fruit-field, and integration of primary, secondary and tertiary industries, and accordingly enhancing the regional ecological function.

2.2 Theoretical analysis of opportunity cost of ecological construction

The resources possessed by a region are limited in time or space, and limited resources have multiple uses. If the resource is used for one purpose, other purposes need to be abandoned. Therefore, resource allocation is selective, and opportunity costs will be incurred when resources are used for one purpose and abandon others. Farmland has multiple functions such as providing daily necessities and ecological environment protection. Therefore, there are many options for the allocation of farmland resources, and any choice will generate opportunity costs. Opportunity costs will be generated when the agricultural production uses of land resources are changed to ecological environmental construction uses. Whether using land to plant food crops and economic crops to develop agriculture, or returning farmland to afforestation and planting grass for ecological environment construction, it will generate opportunity costs. According to the principle of opportunity cost, land is allocated between agricultural industry and ecological construction, the opportunity cost of increasing the output value of any one purpose will reduce the loss of output value of another purpose. In Fig.1, the horizontal axis is the ecological construction output value (

F

), the vertical axis is the agricultural output value (

G

), and the production possibility boundary (

CD

) represents the maximum possible output value combination of using limited land to manage the agricultural industry and ecological construction. From point

E

to point

H

on the production possibility curve in Fig.1, the opportunity cost of expanding the scale of ecological construction and obtaining more

F

F

units of ecological value is to give up

G

G

units of agricultural output value from agricultural operations. If the opportunity cost is small, it means that the larger the scale of ecological construction in the resource allocation, the greater the overall benefits obtained.

Fig.1 Agricultural production and ecological construction boundary

2.3 Theoretical analysis of ecological construction externality

If the land operation entities change the development of agricultural industry to the ecological construction of afforestation and grass planting, the overall benefits will be improved. The overall benefits of ecological construction can be enjoyed by all surrounding people without paying any cost. Therefore, ecological construction produces positive externalities.

2.3.1

Resource allocation of ecological construction under positive externalities. If farmland operation takes ecological construction as the purpose, it requires giving up part of the agricultural operating income, that is, generating opportunity costs. People obtaining the overall benefits generated by ecological construction are the vast number of residents in a larger area. Ecological construction produces positive externalities, leading to the failure of the "invisible hand" of the resource allocation market to regulate and control. Therefore, the "visible hand" of the government is required to regulate and control. One of the regulation methods to generate positive externalities is to take the form of subsidies. Fig.2 is a diagram for the allocation of positive external resources generated by ecological construction. The horizontal axis represents the ecological construction scale (such as the restored farmland area), and the vertical axis represents the marginal cost and marginal revenue of ecological construction.

MPR

is the private marginal revenue of ecological construction (

i.e

, market demand curve

D

);

MSR

is the marginal social revenue of the ecological construction scale, it represents the total social revenue of each unit of ecological construction scale.

MPC

denotes the private marginal cost of the ecological construction of the operating entity (supply curve

S

).

Fig.2 Resource allocation of ecological construction under positive externalities

In a perfect competition market, farmland operation entities follow the principle of maximizing benefits, that is, to determine the ecological construction scale based on private marginal revenue equal to private marginal cost. At point

E

, market supply and demand reach equilibrium; when the ecological construction scale reaches

Q

, it is the optimal scale choice. However, ecological construction will generate positive externalities, and the equilibrium point for maximizing social welfare is at point

F

. The ecological construction scale of the operation entity is required to reach the

Q

level, which exceeds the ecological construction scale

Q

that maximizes the benefits of the operation entity. At scale

Q

, the marginal revenue of the operation entity decreases, so the operation entity is unwilling to accept the

Q

ecological construction scale.

Q

-

Q

are the supply gaps of the ecological construction scale of the operation entities. Due to the existence of positive externalities, the ecological construction scale cannot reach the equilibrium of supply and demand in a completely free market competition, that is, market regulation is ineffective, the market is inefficient in resource allocation, accordingly it is difficult to achieve the national ecological governance and protection macro policy goals.

2.3.2

Measures for internalizing the externalities of ecological construction benefits. The above problem of inefficiency in market allocation of resources can only be solved when the private marginal cost of ecological construction is consistent with the social marginal cost or private marginal revenue and social marginal revenue. To achieve the purpose of ecological construction, the external effects of ecological construction can be internalized through effective means of economic compensation.Through compensating the main body of ecological construction, the supply of ecological construction can be increased to the level of social demand. In Fig.3, when the compensation amount reaches the area of the shaded rectangle

P

P

×

HG

, the supply curve

S

moves to the bottom right to

S

′, intersects with the demand curve

D

, and the ecological construction scale (supply) determined by the intersection exactly meets the social maximum demand

Q

, which solves the problem of insufficient supply of ecological construction scale. At the same time, the revenue of the operation entity is the rectangular area of the shaded part

P

P

×

HG

. Thus, through compensation measures, the internalization of the external effects of ecological construction behavior can be achieved.

Fig.3 Compensation measures for the internalization of external effects of ecological construction

Ecological construction promotes operation entities to adjust the structure of the agricultural industry and expand the scale of grassland and woodland. The positive externalities generated by this behavior can be internalized through strategies such as ecological compensation.

2.4 Analysis of Pareto optimality theory of ecological construction compensation

When the economy’s resource allocation reaches the Pareto optimality, any changes will result in losses. Therefore, the Pareto optimality is also called economic efficiency. Satisfying the Pareto optimality means having economic efficiency, on the contrary, it is lack of economic efficiency.

The Pareto optimality criterion is a measure of the economic efficiency of resource allocation. It is the basis for measuring the efficiency and fairness of resource allocation for changes in behaviors, strategies, and programs. If a measure is implemented to benefit some people, but at least no one is harmed, it means that the original state has not reached the Pareto optimality, there is Pareto improvement, and the implementation of the measure can achieve the goal of improving efficiency.

According to the Pareto optimality theory, although there is a positive externality to the operation entity when implementing the ecological construction behavior, when the operation entity is compensated through the use of ecological compensation measures, the compensation measure has a Pareto improvement. The implementation of ecological construction by operation entities generates positive externalities, but through partial government subsidies, externalities can be eliminated. Therefore, the allocation of ecological construction resources improves the overall benefits of a larger area, and the compensation of operators through ecological compensation measures will not deteriorate the conditions of others. Ecological compensation measures have the effect of Pareto improvement.

3 Comparative analysis of regional ecological construction and industrial economic development opportunity cost

3.1 Basic assumptions and calculation basis for agricultural industrial operation and ecological construction

We first compared the opportunity cost of industrial development and ecological construction, and then made clear prioritizing ecological construction with consideration of industrial development, to provide a quantitative basis for the coordinated development of industry and ecological construction.

3.1.1

Basic hypotheses. Hypothesis 1: The ecological construction strategy is to return farmland to forests and grasslands that are not suitable for planting crops, and the ecological value of forests and grasslands is the total ecological construction value.

Hypothesis 2: Using the unit farmland in Zhangjiakou City to adjust from planting crops to planting forage grass or forest trees, in order to calculate the opportunity cost of farmland for agricultural industry and ecological construction, adjust the unit farmland from crop planting to forage grass planting, then calculate its unit ecological value for calculating the unit opportunity cost.

Hypothesis 3: The unit economic value of forest, grassland and farmland is equivalent, thus comparing opportunity cost only needs comparing the ecological function value of these three.

Hypothesis 4: There are only three uses for farmland: afforestation, planting forage grass, and planting crops. For the allocation of farmland resources among the three, the ecological value of forest and grassland is the opportunity cost of giving up the ecological value of the agricultural industry, and the ecological value of the agricultural industry is the opportunity cost of giving up the ecological construction.

3.1.2

Calculation basis. On the basis of the above hypotheses, with reference to Xie Gaodi’s methodof calculating the value of the unit equivalent factor of terrestrial ecological service function, we calculated the ecological service value of forest, grassland, and farmland. The ecological service value equivalent per unit area of the terrestrial ecosystem is shown in Table 1.

Table 1 Ecological service value equivalent (Cj) per unit area of China’s terrestrial ecosystem

For calculation of the value of unit equivalent factor (

E

) (yuan/ha), we referred to the calculation model of Sun Nengli, and the value model of unit equivalent factor is shown in Formula (1).

(1)

where

E

denotes the value of the unit equivalent factor (yuan/ha);

i

is the type of crop;

p

is the national average price of the

i

crop (yuan/kg);

q

is the yield per unit of the

i

crop (kg/ha);

m

is the sown area of the ith crop (ha);

M

is the sown area of

n

crops (ha).

3.2 Calculation results of ecological value of agricultural, forestry and pastoral land

Based on the above model, we calculated the value of the equivalent factor of various crops in Zhangjiakou, for facilitating to obtain the value of the unit equivalent factor of the ecosystem

E

(yuan/ha). According to Formula (1), the equivalent factor value

E

of the farmland per unit area of cultivated land in Zhangjiakou in 2019 was 21 996 yuan/ha. Based on the product of various ecological function equivalent factor coefficients

C

and the average value of unit equivalent factor

E

in Table 1, we calculated the theoretical ecological value per unit of various types of land in the agricultural industry system. Table 2 shows the calculation results of the theoretical ecological unit value of different uses of land.Since there was no wetland and water body statistics in the statistical data of Zhangjiakou City, we only calculated the ecological environment function value equivalent per unit area of woodland, grassland, and farmland based on various land value equivalent coefficients (Table 2). The crops involved in the calculation of the ecological function value of farmland land use included foxtail millet (Setaria italca), wheat (

Triticum

eastirum

), maize (

Zae

mays

), oats (

Avena

sativa

), rapeseed (

Brassica

napus

), sunflower seeds (

Helianthus

annuus

L.), flax (

Sesamum

indicum

), soybean (

Glycine

max

(Linn.) Merr.), potato (

Solanum

tuberosum

L), Chinese cabbage (

Cruciferae

), celery (

Apiumgraveolens

L.), cabbage (

Brassica

oleracea

L.), spinach (

Spinacia

oleracea

Linn.), and tomatoe (

Solanum

lycopersicum

). During the calculation, in the

Economic

Yearbook

of

Zhangjiakou

City

, the sown area and yield of wheat were not counted, but some data in the sown area and yield of grain did not determine the type of crop. This part of the unclassified scale and yield data was related to wheat. In other words, the data of wheat represent the data of other grains. The unit prices of sunflower seeds and flax seeds were not found in the statistical data

Compilation

of

Cost

-

Benefit

Data

of

China

’

s

Agricultural

Products

, we adopted the average selling prices of various crops that year. As indicated in Table 2, woodland has the largest ecological value in terms of natural ecology, such as gas regulation, climate regulation, soil protection, and biodiversity conservation, as well as in terms of raw materials and entertainment culture. Grassland follows and farmland is lower than the former two in these aspects. Farmland has the greatest ecological value in terms of food production.

Table 2 Ecological function value per unit area of different land use (Cj Ea)

3.3 Comparison of opportunity cost of agricultural industry economy and ecological construction

According to the calculation results in Table 2, if the ecological function value of farmland used for planting crops was 151 992 yuan/ha, the ecological function value of farmland used for afforestation was 480 613 yuan/ha, and the ecological function value of farmland used for planting forage grass or pasture is 159 039 yuan/ha. According to the principle of opportunity cost, if farmland has three uses, it can be used for the development of agricultural industry to grow crops, plant forage or feed to provide material conditions for the breeding industry, and it can also plant trees and afforestation to improve the ecological environment. These three uses will generate opportunity cost, and the opportunity cost of choosing one use is the highest value of the benefits obtained by giving up the other two uses. Therefore, when farmland is used for the development of agricultural industry, giving up both afforestation and forage grass planting, the opportunity cost is the highest value of afforestation and forage grass, and the value of afforestation and forage grass is represented by its ecological value. Based on the above basic hypotheses, using the ecological value of the three to compare, the opportunity cost of developing agricultural industry is:

C

=480 613-151 992=328 621 yuan/ha, the opportunity cost is high.If there are two uses for farmland to choose, that is, to choose between planting crops to develop the agricultural industry and planting forage grasses to develop the breeding industry, the opportunity cost of choosing to develop the agricultural industry is to give up the ecological value of planting forage. Then, the opportunity cost is:

C

=159 039-151 992=70 470 yuan/ha. Although it is less than the opportunity cost of giving up afforestation, in addition to the ecological value of planting forage in the ecological environment, it can also sell forage feed to obtain economic value (assuming that the value is equivalent to the economic value of the agricultural industry). If forage feed is put into the breeding industry, it can also have greater value-added in the production and processing links of the breeding industry. Therefore, in the agro-pastoral ecotone, whether farmland is used to develop forestry or grass industry, its opportunity cost is lower than that of agricultural industry, that is, the opportunity cost of ecological construction in the region is lower than the opportunity cost of agricultural industry development.

4 Recommendations

4.1 Establishing a comprehensive agricultural industry system prioritizing the ecological development

The behaviors that should be implemented based on the level of farmland land operators include: adjusting the industrial structure, extending the industrial space layout, extending the industrial chain, broadening the industrial boundary, building a multi-kinetic energy system of the agriculture, animal husbandry and forestry industries, and integrating the primary, secondary and tertiary industries to give full play to the multiple functions of woodland, grassland, and farmland. Through Pareto improvement, it is expected to improve the efficiency of resource allocation, and achieves the purpose of improving the ecological environment, enhancing economic benefits, and expanding social benefits.

(i) Adjusting the structure of farmland, forest and grassland, and establishing a comprehensive industrial system that makes full use of the spatial resources of arbors, shrubs, and grassland. It is recommended to adjust the structure of agricultural land, expand the scale of woodland and grassland, reduce the area of low-yield fields, build a comprehensive industrial system for the use of arbor, shrub and grass space, and promote the comprehensive three-dimensional resource allocation of the space utilization of arbor, shrub and grass in regional farmland. Through properly arranging the spatial structure of farmland, woodland, and grassland, it is recommended to develop a three-dimensional spatial model of characteristic arbors, shrubs, and forage, and develop understory planting and breeding, so as to make full use of space, transform resource advantages into economic advantages, and improve ecological environment.

(ii) Adjusting the structure of grain and forage feed land and building an industrial system of planting and breeding with vertical and horizontal integration of ecological resource recycling. Through the "grain-to-feed" strategy, planting forage in farmland can provides material conditions for the breeding industry. It is recommended to establish an industrial system of planting and breeding with vertical and horizontal integration of ecological resource recycling, integrating forage planting and processing, livestock and poultry breeding, livestock product processing and sales, and manure treatment in a vertical and horizontal integrated recycling system, which can not only ensure the quality and safety of forage and feed and processed animal products, but also reduce the production, transaction and transportation costs of the operation entities, and can improve the ecological environment of agriculture and animal husbandry and increase the added value of each link.

(iii) Adjusting the characteristic agricultural structure and establishing an operation system integrating production, sales, and tourism of primary, secondary, and tertiary industries. Through adjusting the "grain-to-feed" structure in the planting industry, and increasing the scale of characteristic crop planting, it is recommended to establish an operation system integrating production, sales, and tourism of primary, secondary, and tertiary industries, extend the industrial chain of green agriculture, animal husbandry and forestry products, and develop special agricultural production and tertiary industry integration management, so as to production and transaction costs, increase product added value, and ultimately improve economic and ecological benefits.

4.2 Establishing and improving the incentive mechanism for ecological construction

Governments at all levels should eliminate the positive externalities of ecological construction and promote ecological priority construction by establishing relevant incentive mechanisms.

(i) Establishing a subsidy incentive mechanism for woodland and grassland to replace farmland. Based on the conclusion that the opportunity cost of woodland and grassland operation is lower than that of farmland operation, the woodland and grassland operators in the study area account for a larger proportion of the woodland and grassland operation, and the structural adjustment behavior of the smaller farmland has a positive externality. Thus, governments at all levels should establish a continuous ecological compensation system to encourage ecological construction.

(ii) Establishing a subsidy incentive mechanism for integrated agriculture and animal husbandry operations. The planting industry based on the integration of agriculture and animal husbandry and the integrated operation of planting and breeding provides materials for the breeding industry. The organic fertilizer made from livestock and poultry manure in the breeding industry provides fertilizer for the planting industry and provides the livestock products to the food processing industry. These can reduce the production cost of agriculture and animal husbandry, improve the ecological environment, increase the added value, and ensure the quality of raw materials in the upstream of food processing, and also improve economic and ecological benefits. Thus, governments at all levels should establish an incentive mechanism for integrated operation of agriculture and animal husbandry and the extension of the integrated operation of planting and animal husbandry to encourage ecological priority development.

(iii) Establishing an incentive mechanism integrating characteristic agricultural product marketing and tourism. The integrated operation of characteristic agricultural product marketing and tourism can solve the resource competition contradiction with ecological construction, and increase the profit of various links in the agricultural industry. Therefore, governments at all levels should guide agricultural industry operators to vigorously increase the production and processing of characteristic agricultural products, expand the scale of characteristic agricultural operation, and enhance market competition in characteristic agricultural industries through establishing incentive mechanisms such as financial subsidies, preferential credit and financing.

5 Discussion and prospects

Located in the northern agro-pastoral ecotone, Zhangjiakou City has the characteristics of staggered distribution of farmland and grassland, equal status of agriculture and animal husbandry, vulnerable regional ecological environment, and underdeveloped economy. In addition, it serves as an ecological barrier in the Beijing-Tianjin-Hebei region and is responsible for the important task of construction of the two districts of the capital. In this region, there are conflicts between agricultural industry and ecological construction resource competition, and there are also problems that need to be solved urgently for economic growth and continuous ecological improvement. Using the theory and empirical analysis methods, we compared the opportunity costs of agricultural industry development and ecological construction in the study area. The results indicate that, for the selection of limited farmland resources between ecological construction and industrial development, the opportunity cost of ecological construction is relatively small, the value of ecological function is relatively large, and the comprehensive benefits are relatively high. This conclusion provides a theoretical and empirical basis for the strategy of prioritizing the ecological construction with coordinated development of industries, and is expected to provide reference for further study of prioritizing the ecological construction with consideration of agricultural industry development in the northern agro-pastoral ecotone.