Driving Force Analysis of the Agricultural Water Footprint in China

Oct 7, 2014 - Driving Force Analysis of the Agricultural Water Footprint in China. Based on the LMDI Method. Chunfu Zhao and Bin Chen*. State Key Join...
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Driving force analysis of the agricultural water footprint in China based on the LMDI method Chunfu Zhao, and Bin Chen Environ. Sci. Technol., Just Accepted Manuscript • DOI: 10.1021/es503513z • Publication Date (Web): 07 Oct 2014 Downloaded from http://pubs.acs.org on October 7, 2014

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Driving force analysis of the agricultural water footprint in China based on the LMDI method Chunfu Zhaoa, Bin Chena,*,§ a

State Key Joint Laboratory of Environmental Simulation and Pollution Control, School of Environment, Beijing Normal University, Beijing 100875, P R China

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ABSTRACT

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China’s water scarcity problems have become more severe because of the unprecedented

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economic development and population explosion. Considering agriculture’s large share of water

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consumption, obtaining a clear understanding of Chinese agricultural consumptive water use plays

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a key role in addressing China’s water resource stress and providing appropriate water mitigation

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policies. We account for the Chinese agricultural water footprint from 1990 to 2009 based on

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bottom up approach. Then, the underlying driving forces are decomposed into diet structure effect,

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efficiency effect, economic activity effect, and population effect, and analyzed by applying a

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log-mean Divisia index (LMDI) model. The results reveal that the Chinese agricultural water

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footprint has risen from the 94.1 Gm3 in 1990 to 141 Gm3 in 2009. The economic activity effect is

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the largest positive contributor to promoting the water footprint growth, followed by the

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population effect and diet structure effect. Although water efficiency improvement as a significant

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negative effect has reduced overall water footprint, the water footprint decline from water

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efficiency improvement cannot compensate for the huge increase from the three positive driving

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factors. The combination of water efficiency improvement and dietary structure adjustment is the

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most effective approach for controlling the Chinese agricultural water footprint’s further growth.

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Keywords: LMDI, Water footprint, China’s agricultural sector

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1. INTRODUCTION

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China’s freshwater resources are subject to increasing pressure owing to water shortage

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and pollution.1 In recent years, rapid economic development and urbanization coupled with a

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growing population, poor water resource management, and uneven spatial distribution have

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increased the frequency and severity of water-related crises in China.2-8 As a sector with high

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water intensity, Chinese agriculture has a large share of water consumption, accounting for 73.8%

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of the total water use in 2011.9-11 Accordingly, a clear understanding of water consumption for

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agriculture is essential to addressing current water problems and formulating water resource policy

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in China. However, the government has generally taken a purely national perspective to managing

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domestic water resources, with the goal of using domestic water supply to meet the final

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demand.12-20 Under the backdrop of globalization, international trade has created a linkage of

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water resource utilization among different countries, providing an opportunity for countries with

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scarce water resources to meet their water demand by importing water-intensive products.21 As a

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result, conventional water resource accounting should be broadened to account for water

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embodied in a nation’s imports and exports.

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The concept of water footprint was initially introduced by Hoekstra and Hung in 200222

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and subsequently improved by Chapagain and Hoekstra in 2003.23 Analogous to the ecological

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footprint concept,22 the water footprint is defined as the total volume of water used, directly or

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indirectly, to produce the goods and services consumed by the inhabitants of a certain

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geographical region.24 The water footprint as a measure of human’s appropriation of fresh water

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resources evolved from the concept of virtual water initially proposed by Allan (1993)25 when

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studying the potential methods to alleviate water scarcity in the Middle East and was defined as

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the volume of water required to produce a commodity or service.26 According to the water

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footprint definition put forth by Hoekstra et al., the main difference between virtual water and

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water footprint lies in their being defined from the perspectives of production and consumption,

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respectively, even though the water footprint content of a product is numerically equal to the

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content of virtual water.27 It should be noted that the water footprint concept described by

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Hoekstra et al. reflected the quantity of consumptive water use without an estimation of the related

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environmental impacts. Such a volumetric water footprint concept cannot address the issue of

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water availability, or scarcity.28 Recently, Ridoutt et al. incorporated the water stress

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characterization factors to improve the water footprint calculation within the context of life cycle

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assessment (LCA).29, 30 The ISO 14046 standard for the water footprint has also been compliant

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with LCA principles (ISO/TC207/SC5/WG8).31 Despite the two communities being somewhat in

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conflict in the past few years, both water footprint concepts have distinguished water consumption

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for creating export from that associated with production of goods for domestic consumption. In

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addition, both approaches include the consumption of water associated with imported products

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produced in foreign countries and consumed by domestic inhabitants. Therefore, water resources

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accounting from the water footprint perspective can expand traditional water resource accounting,

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which has focused on the water consumption within their own territory, to consideration of

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consumption of water associated with international trade.

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In general, there are two alternative approaches to calculating the water footprint: the

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bottom-up water footprint accounting approach based on detailed process information and the

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top-down approach based on input-output techniques.32,

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The bottom-up approach employs

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detailed process data to estimate the virtual water content embedded in internationally traded

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goods and services. The water footprint is the sum of the goods and services consumed by a

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country multiplied by their corresponding virtual water content. The bottom-up approach suffers

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from following the shortcomings: it cannot distinguish intermediate water use from final water use,

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and it is mainly applied to calculate water footprint in agricultural sector, but lacks detailed

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calculation for the industry and service sectors. However, because of the simplicity and relatively

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good data availability, the bottom-up approach has become a popular method to calculate the

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virtual water of products or the water footprint within a geographically delineated area. For

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example, Chapagain and Hoekstra conducted studies to calculate the virtual water of coffee, tea,

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rice, wine, soy milk, tomatoes and meat.34-38 As an extensively used top-down approach, the

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input-output model has also been commonly employed to analyze the issue of virtual water in

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previous studies at the regional, national and global scales.39-43 The input-output model can

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distribute all of the direct water consumption into each sector of the whole economy to reflect the

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water flow across sectors: however, this technique is often too rough to conduct concrete

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assessments for some specific products or techniques due to the high level of aggregation.44 To

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combine the strengths and reduce the weakness of both methods, Shao and Chen developed a

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hybrid method as a combination of process analysis and input-output analysis to assess the water

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footprint of wastewater treatment.45 Although existing studies have provided a water footprint

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assessment for different sectors across regional, national and global scales, few studies have

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investigated the driving forces underlying the changes of water footprint over time.46

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To understand the key factors that influence the change of Chinese agricultural water

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footprint, methods that identify the driving forces for such a change should be employed. Structure

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decomposition analysis (SDA) and index decomposition analysis (IDA) are two commonly used

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methods for the decomposition of indicator changes. Because of the simplicity and flexibility of

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the IDA methodology, it is easy to use and extensively applied compared with the SDA method.47

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IDA can be further divided into the Divisia index decomposition technique and Laspeyres index

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decomposition technique.48 During the evolution of IDA method, a range of decomposition

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techniques have been established, among which LMDI, initially developed by Ang (2004)47 based

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on the Divisia index, is considered to be a suitable approach. The main advantage of LMDI is that

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it includes perfect decomposition, consistency in aggregation, and the ability to handle zero values

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with no unexplained residual terms. Therefore, this approach has been extensively applied with

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carbon dioxide, energy efficiency, and energy-related studies at the industrial level47, 49-51 and

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national level.52-54 However, according to the best of our knowledge, few studies have applied

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such a decomposition model to water footprint related issues.55 Therefore, the objective of this

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paper is to fill in this gap by employing LMDI to analyze the driving force underlying the change

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in the agriculture sector’s water footprint. For this purpose, we first account for the water resource

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consumption in Chinese agriculture from the water footprint perspective. Then, we explore the

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driving force for such water footprint changes by decomposing the factors that have affected the

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change of Chinese agricultural water footprint into diet structure effect, efficiency effect,

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agricultural economic activity effect, and population effect. Finally, some policies aimed at

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alleviating China’s domestic water resource pressure are proposed.

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2. METHODOLOGY

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2.1 China’s agricultural water footprint accounting framework

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The water footprint accounting in this study is based on a bottom-up approach, which

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estimates the Chinese agricultural water footprint ( WFChi , agr ) by multiplying all agricultural

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products consumed by Chinese inhabitants by their respective product water footprint:

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WF = Chi , agr

∑ C ( p) ×WF

prod

( p)

(1)

p

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where C ( p ) is the final consumption of agricultural product p by consumers within China

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and WFprod ( p ) is the water footprint of this product. Considering that product p partly

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originates from China and partly from other countries through international trade, the average

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water footprint of p can be estimated by the following equation:

SChi ( p ) *WFChi + ∑ ( M ne ( p ) *WFne )

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WFprod ( p ) =

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where SChi ( p ) refers to the domestic supply quantity of product p from China, while WFChi

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denotes the water used to produce product p in China. M ne ( p ) refers to the import quantity

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of product p from country ne , while WFne is the water consumption to produce product p

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in country ne . The import origin of product p was traced by FAO database and corresponding

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WFne was extracted from Mekonnen and Hoekstra.56 A more detailed description of the data is

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provided in the Supplementary Information (SI).

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2.2 Calculation of the water footprint

ne

SChi ( p ) + M ne ( p )

(2)

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Considering the diversity of the commodities in the agricultural sector, we selected 34 crop

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products and 6 livestock products that make significant contributions to the overall water footprint

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of China’s agricultural sector as the scope of the present study. These food terms can be

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categorized into six groups, i.e., cereals (rice, wheat, maize and sorghum), cash crops (soybean,

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cotton, groundnut, sunflower, sugar beet, tea, coffee and potatoes), crop processed products (wine,

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beer of barely, cottonseed oil, groundnut oil, maize oil, palm oil, sesame oil, soybean oil and

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sunflower oil), fruit (apples, bananas, oranges, and other fruits), vegetables (onions, tomatoes and

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other vegetables), and livestock (beef, mutton and goat meat, poultry meat, pork, milk and eggs).

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Water used during production of a specific agricultural product can be divided into

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consumptive and degradative use.57 Consumptive water use or consumption commonly refers to

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water withdrawals that evaporate are incorporated into products, consumed by animals, transferred

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into different watersheds, or disposed of in the sea after use.57-59 Consumptive water can be further

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categorized into green and blue components. Blue water refers to the volume of surface and

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groundwater consumed (evaporated) during production of a good, while green water is the amount

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of rainwater (stored in the soil as soil moisture) used by plants. In this study, we focused on

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consumptive use for China’s agricultural sector, and excluded green water because it does not

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contribute to water scarcity. Blue water consumption of each agricultural product in this study was

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extracted from Mekonnen and Hoekstra56, which is estimated by the global average agricultural

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product virtual value from 1996 to 2005. Since the Chinese government has made great efforts to

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improve the agricultural water productivity during the research period, a constant water footprint

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value may overestimate the total water footprint. Therefore, we further adjusted the water footprint

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value extracted from Mekonnen and Hoekstra by taking both the yield and irrigation area into

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account (a detailed description can be found in the Methodology section of SI).56

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2.3 LMDI methodology

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The LMDI initiated by Ang (1998) with zero residual errors was employed to analyze the

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driving force behind changes in the Chinese agricultural water footprint in this study.60 Water

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footprint consumption in a certain country has been shown to be highly related to factors of water

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use efficiency, diet structure, agricultural economic development, and population.3, 11 Thus, the

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effects of structure, efficiency, agricultural economic activity, and population were selected as

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potential factors to decompose changes in the Chinese agricultural water footprint. The following

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IDA identity describes the total water footprint consumption:

151 = W

Wi W G

P ∑ S TEP ∑= W G P i

i

(5)

i

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where W denotes the total water resource consumption for agriculture; Wi is the water footprint

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of the i th group, where i =1, 2, ... 6, denoting cereals, cash crops, crop processed products, fruit,

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vegetables, and livestock, respectively; G refers to the agricultural GDP; P is the population

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size; Si =

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efficiency; E =

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economic development and is measured by the ratio of agricultural GDP to population size.

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Details regarding the calculation of decomposition factors are shown in the SI.

Wi W represents the water footprint structure; T = refers to agricultural water G W

G represents agricultural economic activity, which reflects the agricultural P

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The LMDI can be divided into additive decomposition and multiplicative decomposition;

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however, the two decomposition methods display similar results. Because the additive

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decomposition approach is easier to use and interpreted compared with multiplicative

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decomposition, the following additive decomposition was employed:

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W = W T − W 0 = Wstr +Weff +Weco +W pop

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where,

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The degree to which each effect contributes to the change in the water footprint of China’s

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agriculture sector was estimated by the following equations:

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Wstr = ∑

WiT − Wi 0 Si T ln ln WiT − ln Wi 0 Si 0

(7)

Weff = ∑

WiT − Wi 0 IT ln ln WiT − ln Wi 0 I 0

(8)

W T and W 0 are the water consumption during the period T and 0 , respectively.

i

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i

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WiT − Wi 0 CT Weco ∑ ln 0 0 T C i ln Wi − ln Wi

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W pop = ∑ i

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(6)

WiT − Wi 0 PT ln ln WiT − ln Wi 0 P 0

(9)

(10)

2.4 Data description

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The research period starts in 1990 and ends in 2009. The agricultural products consumption

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in this study was extracted from the Food Balance Sheets (FBS) of the FAO database.61 Both the

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GDP data of agriculture and population were obtained from the World Bank Database.62 To

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remove the effects of price changes, we adjusted the GDP at the current price to the GDP at a

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constant price for the year of 2000 according to indices of GDP that were obtained from the China

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Statistical Yearbook (CSBC, 1990-2009).63 A detailed description of the data was provided in the

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“data source” section of the SI.

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3. RESULTS

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3.1 Water footprint accounting

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Fig. 1 Total water footprint consumption and corresponding composition of China’s agricultural sector

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As shown in Fig. 1, the water footprint in China’s agriculture sector in absolute terms has

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increased rapidly from 1990 to 2009. The aggregate of the water footprint has increased from 94.1

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Gm3 in 1990 to 141.1 Gm3 in 2009 with an average annual growth rate of 2.21%. The composition

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of the Chinese agricultural water footprint has also changed significantly during the research

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period. In 1990, the water footprint of cereals accounted for 74.65% of the total water footprint;

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however, this value decreased to 53.44% in 2009. This decrease was primarily a result of the

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increasing water footprint share of livestock from 16.29% in 1990 to 33.62% in 2009. The share of

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the water footprint for crop processed products, fruits, and vegetables show a relatively slow

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increase when compared with livestock during the research period, which has increased from

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1.57%, 1.89%, and 0.53% in 1990 to 4.17%, 3.69%, and 1.45% in 2009, respectively.

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3.2 Decomposition analysis

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The aggregate decomposition results are listed in Fig. 2. The economic activity, population,

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and diet structure are positive effects that have led to a significant increase in the overall Chinese

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agricultural water footprint from 1990 to 2009, while improvements in agricultural water

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productivity have acted as negative factors that inhibited such an increase. Among the three

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positive factors, the economic activity is the most important contributor to growth of the Chinese

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agricultural water footprint, followed by the effects of population and diet structure. Although the

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efficiency effect is the largest negative factor leading to reduction of the overall water footprint for

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China’s agricultural sector from 1990 to 2009, the water footprint reduction owing to the

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efficiency improvement cannot offset the increase in the water footprint originating from the

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effects of economic activity, population and diet structure. Therefore, the total water footprint

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from China’s agriculture sector presents an increasing trend over the period of 1990–2009. 8.00E+010

Water footprint change (m3)

6.00E+010 4.00E+010

Diet structure effect Efficiency effect Economic activity effect Population effect Total water footprint change

2.00E+010 0.00E+000 -2.00E+010 -4.00E+010

1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009

-6.00E+010

206 207

Year

Fig. 2 Aggregate decomposition of change in water footprint in China’s agricultural sector

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3.2.1 Diet structure effect

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Overall, diet structure exerted a weak positive effect, pushing forward the growth of the

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Chinese agricultural water footprint. The accumulative structure effect resulted in an increase of

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the water footprint by 0.011 Gm3, accounting for the 0.01% total change in absolute value.

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Although the overall contribution of the diet structure effect to the total water footprint change is

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limited, the pattern of the water footprint makeup at the group level showed a large change from

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1990 to 2009 (Fig. 3). Therefore, we examined the accumulative contribution of the structure

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effect at the group level. As shown in Fig. 3, the accumulative contribution of each group’s

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structure effect reveals that adjustment of the structure in response to consumption of agricultural

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products has led to an accumulative decrease in the water footprint of cereal to 25.7 Gm3 in 2009.

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However, the reduction of the accumulative water footprint from cereal over the study period was

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neutralized by the accumulative water footprint increase from the other five groups, particularly

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livestock. More specifically, the cumulative water footprint increase from livestock over the study

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period reached 21 Gm3, which nearly offset the decrease in the water footprint from cereals. 3.00E+010

Cereals Cash crops Crop processed products Vegetables Fruit Livestock

Water footprint change (m3)

2.00E+010

1.00E+010

0.00E+000

-1.00E+010

-2.00E+010

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2008

2007

2006

2005

2004

2003

2002

2001

2000

1999

1998

1997

1996

1995

1994

1993

1992

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1991

-3.00E+010

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Water footprint change (m3)

-5.00E+009 -1.00E+010 -1.50E+010 -2.00E+010 -2.50E+010

224 225

-3.00E+010

Cereals Cash crops Crop processed products Vegetables Fruit Livestock

Fig. 4 The accumulative contribution of each group’s efficiency to water footprint

226 227

2007 2008 2009

0.00E+000

2003 2004 2005 2006

Fig. 3 The accumulative contribution of diet structure to water footprint change 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002

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change 3.2.2 Efficiency effect

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The efficiency effect is the only force mitigating the agriculture sector-related water footprint

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at the aggregate level. The cumulative efficiency effect has led to a decrease in the water footprint

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of 45.6 Gm3, which accounts for 32.98% of the total change in the water footprint based on the

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absolute value. At the group level (Fig. 4), cereals are the most important contributor to the overall

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effect improvement, followed by livestock and cash crops with cumulative contributions of 29.1

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Gm3, 11.5 Gm3 and 1.79 Gm3 in absolute value, respectively. The contribution of the previous

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three types of agricultural products reached 16.8 Gm3, accounting for 93.05% of the total

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efficiency contribution. The other three types of agricultural products (vegetables, fruits, and crop

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processed product) also showed a weak negative driving force; however, their absolute value

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accounted for only 6.95% of the total efficiency improvement.

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3.2.3 Economic activity effect

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Despite the growing importance of industry in China, the agricultural sector is still essential

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to China’s food security. Chinese agricultural economic growth was lower than that of the rest of

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economy during the research period, but its performance was still impressive. Specifically, from

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1990 to 2009, China’s agricultural GDP increased from 981.4 billion RMB to 2167.7 billion RMB,

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which undoubtedly resulted in large water consumption to meet agricultural demand. The

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decomposition results demonstrate that economic activity effect was the largest positive factor

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driving continuous growth of the water footprint during 1990–2009. As shown in Fig. 5, the

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cumulative effect of the economic activity resulted in a 74.6 Gm3 increase in the water footprint at

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the aggregate level, accounting for 53.99% of the total change in the absolute value of the water

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footprint associated with China’s agricultural sector over the research period. A more detailed

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group disaggregation indicated that the economic activity effect stimulated each group’s water

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footprint consumption over the entire period (Fig. 5). Among the six types of agricultural products

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examined, the cumulative economic activity effect of cereal was the largest contributor to the total

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change in the water footprint associated with economic activity, followed by livestock, cash crops,

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fruit, processed crop products, and vegetables, which showed cumulative increases of 47.9 Gm3,

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18.6Gm3, 2.84 Gm3, 2.20 Gm3, 2.16 Gm3, and 0.85 Gm3, respectively, from 1990 to 2010.

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Moreover, the increase associated with economic output for each group except cereal was

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relatively weaker before 2004, and the water footprint growth from the economic activity effect

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increased rapidly after 2004. The fact that economic growth has had a growing influence on

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consumption associated with the water footprint since 2004 indicates that it is crucial to proper

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coordination of the relationship between economic development and water resource consumption

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in the agricultural sector.

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3.2.4 Population effect

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China’s population increased from 1.14 billion in 1990 to 1.33 billion in 2009. The

263

agricultural sector is essential to meeting the basic requirements and supporting the survival of the

264

population; accordingly, population effects acted as a positive driving factor promoting the water

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footprint consumption for Chinese agriculture at either the aggregate level or group level from

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1990 to 2009 (Fig. 6). At the aggregate level, the cumulative contribution from the population

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increased by 18 Gm3 over the research period, accounting for 13.02% of the total change in the

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water footprint. Furthermore, the increasing trend at both the aggregate and group level indicates

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that the cumulative increase from population growth gradually slowed over the research period,

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which is closely related to the enforcement of family planning in China. Although the family

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planning policy slowed increase in the water footprint associated with the population effect, this

272

effect is still an important positive driving factor in the continuous promotion of the water

273

footprint increase owing to the large population base in China.

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5.00E+010

Cereals Cash crops Crop processed products Vegetables Fruit Livestock

4.00E+010

Water footprint change (m3)

3.00E+010

1.00E+010

1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009

1.00E+001

274 275

Y Fig. 5 The accumulative contribution of each group’s economic activity effect to changes

276

in the water footprint

1.20E+010 1.00E+010

Water footprint change (m3)

8.00E+009

Cereals Cash crops Crop processed products Vegetables Fruit Livestock

6.00E+009

4.00E+009

2.00E+009

278 279

2009

2008

2007

2006

2005

2003 2004

2001 2002

2000

1998 1999

1997

1995 1996

1994

1992 1993

277

1991

0.00E+000

Fig. 6 The accumulative contribution of each group’s population effect to changes in the water footprint

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4. Discussion

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4.1 Change in water footprint associated with China’s agricultural sector

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China’s agricultural sector’s water footprint increased from 1990 to 2009. The structure of the

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Chinese agricultural water footprint also changed significantly during the research period. Cereal

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had the greatest effect on the total water footprint over the study period; however, this position

285

was weakened by the rising proportion of livestock products, processed crop products, fruits, and

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vegetables, particularly livestock products. The transformation of the Chinese agricultural water

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footprint structure coincides with changes in the observed food consumption patterns.61 Since

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1990, the consumption of cereals has decreased, whereas consumption of livestock, processed

289

crop products, vegetables, and fruits has risen rapidly during this period. This shift in food

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consumption towards meat is mainly due to the rapid increase in per capita income, urbanization

291

and market expansion.3 Considering that meat requires more water to produce per calorie, China’s

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diet structure has evolved in a more water-intensive direction in the last few decades.11

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The agricultural water footprint structure in China is different from those of European

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countries. For example, the agricultural water footprint of France and the Netherlands is

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dominated by meat consumption, while the proportion of the water footprint corresponding to

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cereal consumption is rather small in these countries.35, 64 This difference in the water footprint is

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owing to the fact that China has a vegetable-rich diet, while European countries are often

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characterized by overconsumption of food and a high proportion of animal products.65

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4.2 Driving force behind changes in the water footprint

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The decomposition results demonstrated that the efficiency effect was the only inhibitory

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effect that compensated for the increase in the Chinese agricultural water footprint over the study

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period. The apparent improvement in water use efficiency can be explained by the effort of the

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Chinese government to implement water-saving technologies and set agricultural policies. In the

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past two decades, the Chinese government has collaborated with international research

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organizations to actively promote adoption of water-saving technologies. The government has also

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provided financial support for construction of agricultural water-conserving infrastructure such as

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drip irrigation systems, sprinkler irrigation systems, and plastic mulches. These policies have

308

accelerated the transition of China’s agricultural industry from traditional extensive agriculture

309

systems to modern precision agriculture systems.66

310

Among the positive effects that have contributed to the increase in the Chinese agricultural

311

water footprint from 1990 to 2009, the agricultural economic growth effect has been the largest

312

driver. Although China’s rapid economic growth has largely been driven by industrialization,

313

many farmers in remote areas are still highly reliant on agriculture to make a living. The desire by

314

many farmers to move out of poverty has increased the rapid development of agriculture, which

315

has significantly driven the increase in the Chinese agricultural water footprint.

316

The population was the second largest driver of the increase in the Chinese agricultural water

317

footprint from 1990 to 2009, and this factor also had a considerable positive effect on the soaring

318

water footprint of China’s agricultural sector. China’s population grew from 1.14 billion in 1990 to

319

1.33 billion in 2009, which has led to a significant increase in water resource pressure. Despite

320

enforcement of a successful population control policy, the population is projected to increase to

321

1.436 billion in 2033 owing to population growth inertia.67 Thus, there remains an urgent need for

322

China’s water resource system to produce a large amount of agricultural products to support such a

323

large population in the next 10 years.

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324

As the third largest driver of the increase in the Chinese agricultural water footprint from

325

1990 to 2009, the effects of structure on the increase in the water footprint is limited. However, a

326

dramatic shift in the food consumption patterns towards being meat intensive occurred in China

327

over the study period.3 The rapid economic growth and urbanization in China over the last two

328

decades have significantly increased consumer incomes, which has undoubtedly resulted in a more

329

meat-intensive food consumption pattern because food consumption is closely related to affluence,

330

urbanization, and cultural food preferencs.68 Although additional meat consumption has stimulated

331

the increase in the water footprint, most of that increase has been offset by the reduction in the

332

water footprint owing to decreased demand for cereals. Thus, the overall structural effect only led

333

to a weakly positive effect on increasing the Chinese agricultural water footprint.

334

4.3 Implications for future planning by the Chinese agricultural sector

335

Investigation of the Chinese agricultural water footprint from 1990 to 2009 and in-depth

336

analysis of the driving forces that contributed to changes in the footprint are essential to decision

337

makers developing countermeasures and implementing strategic planning to mitigate China’s

338

current water resource pressure. Based on the results of water footprint accounting and analysis of

339

the driving forces that contributed to the change in the water footprint of China’s agriculture sector,

340

there are several strategies available to address the current impacts of agriculture food

341

consumption on water use.

342

Water use efficiency improvement is an option to alleviate the current water resource pressure.

343

Indeed, a marginal reduction in irrigation water use can release substantial amounts of water for

344

expansion of agriculture, as well as for meeting the demand of other sectors.69 Although China’s

345

water use efficiency in the agricultural sector improved over the study period, the water use

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346

efficiency is still low when compared with other industrialized countries owing to inappropriate

347

irrigation management practices and lower investments in infrastructure construction.66 Therefore,

348

there is still a large opportunity to further improve water use efficiency. Over the past two decades,

349

large investments in China have been used to promote the development of water-saving

350

technology, such as drip irrigation, sprinkler irrigation, and plastic mulches. However, there is

351

little evidence of the widespread adoption of water-saving technologies in China’s agricultural

352

production system.70 This is primarily because farmers do not directly benefit from the water

353

savings.71 The inefficient use of water resources is rooted in the fact that water is a common-use

354

resource; therefore, some effective measures may be taken to address the externalities of water

355

resource use and encourage farmers to adopt water-saving technologies. However, the Chinese

356

government has put more emphasis on efforts to construct a ‘water-saving society’ and improve

357

agricultural water use efficiency in the past, while few measures have addressed the externalities

358

of agricultural water use.4 Despite some polices such as reforming of the irrigation water price to

359

deal with the externalities of irrigation water consumption, these policies have not been

360

implemented in most locations owing to political reasons.72 Additionally, a water rights system by

361

allocating available water supplies for beneficial uses in an orderly manner may also improve the

362

water use efficiency, because freely traded, legally enforceable water rights can provide incentives

363

for farmers to promote efficient water resource allocation.73 Therefore, the pricing mechanism and

364

water rights system could be taken into account to improve water use efficiency in future planning

365

studies.

366

China’s shift toward a meat-intensive diet has had a weakly positive effect on the Chinese

367

agricultural water footprint. The reduction in the water footprint from cereals consumption has

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368

been offset by the increase from meat and dairy products. Despite the rapid increase in the

369

consumption of meat, China’s per capita annual meat consumption is still lower than that of Japan,

370

South Korea, and Malaysia; nevertheless, it is expected to continue to grow to rival that of Europe

371

and the United States, which will put further pressure on China’s domestic water resources.74 To

372

respond to the water resource pressure induced by a meat-intensive diet structure, greater attention

373

should be paid to optimization of residents’ lifestyle with less livestock consumption. The

374

reduction in the water footprint of Austria and the EU in response to diet structure optimization

375

has demonstrated that a vegetarian diet will result in a lower water footprint than the current diet

376

and a healthy diet.75, 76 Indeed, live animals consume a large amount of feed crops, drinking water,

377

and service water in their lifetime, so meat products will require substantially more water per

378

kilogram during production than grains and vegetables.11,

379

water-efficient cereal and vegetable-rich diet is a promising way for China to alleviate the current

380

water resource depletion pressure related to agricultural products consumption. In addition,

381

transformation of the residents’ lifestyles should not only focus on improvement of the diet

382

structure, but also on reducing food losses and waste. Liu et al. demonstrated that over 14% of

383

China’s total blue water consumption consisted of wasted food in 2010. However, this estimation

384

is still conservative because only cereals, vegetables, and fruits have been incorporated into the

385

accounting boundary.77 Therefore, a vegetable-rich diet combined with reduced food losses and

386

waste is likely an effective method to relieve Chinese agriculture-related water resource pressure.

76

Therefore, moving to a more

387

Finally, it should be noted that measures aiming at alleviating Chinese agriculture’s water

388

crisis should not only focus on the domestic water consumption because expanding and optimizing

389

importation of agricultural products may also mitigate Chinese agricultural water resource stress.

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390

The optimization of agricultural imports can directly shift domestic water resource burden to the

391

other regions and transfer high productivity agricultural products to China as well. However, as a

392

developing country, it is unrealistic for China’s local economy to be able to afford large-scale food

393

importation in the short term. In addition, from the perspective of global water resource

394

conservation, the potential for saving water by increased efficiency is an order of magnitude larger

395

than that of global trade optimization11 Therefore, a combination of improved water use efficiency

396

and food consumption are the best prospects for China to alleviate the current agriculture-related

397

water resource stress.

398

It should also be noted that there are uncertainties and limitations to estimations of blue water

399

uses in crop production and the results based on these estimated values. In future studies, the

400

accuracy of the Chinese agricultural water footprint should be improved, which will provide more

401

accurate information for the LMDI. In addition, the spatial heterogeneity for water scarcity in

402

China and import origins should be taken into account to reduce uncertainties regarding the

403

homogeneity of the available data. Nevertheless, this study has bridged an important

404

methodological gap regarding analysis of the driving force of consumption influencing the water

405

footprint at the national scale based on the LMDI.

406

.

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ACKNOWLEDGEMENTS 407

This work was supported by the Major Research plan of the National Natural Science Foundation

408

of China (No. 91325302), Fund for Creative Research Groups of the National Natural Science

409

Foundation of China (No. 51121003), National Natural Science Foundation of China (No.

410

41271543), and Specialized Research Fund for the Doctoral Program of Higher Education of

411

China (No. 20130003110027).

ASSOCIATED CONTENT Supporting Information Available The explanatory details of LMDI methodology, data description, and calculation details of water footprint are presented in the Supporting Information. This information is available free of charge via the Internet at http://pubs.acs.org/. 412

AUTHOR INFORMATION 413

Corresponding author

414

**Tel.: +86−10−58807368; fax: +86−10−58807368; e−mail: [email protected] (Bin Chen).

415

Affiliation: State Key Joint Laboratory of Environmental Simulation and Pollution Control,

416

School of Environment, Beijing Normal University, Beijing 100875, China

417 418

Author Contributions

419 420 421

§Both authors have equal contribution as the first author.

422

The authors declare no competing financial interest.

Notes

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