Understanding ecosystem services in a metacoupled world

Abstract

Driven by intensive globalization and technological development, shifting from place-based research on ecosystem services to an understanding of multiple human and natural interactions within the focal system, as well as between adjacent and distant systems, is becoming an urgent necessity. An integrated framework of metacoupling (socio-economic-environmental interactions within and across borders) is proposed to address this shift. Here, I have demonstrated the utility of the metacoupling framework, which includes intracoupling, pericoupling, and telecoupling, in the assessment of ecosystem services. I have referred to three examples from China (water supply, soybean production and trade, banana planation and displacement). I have also provided regulations and cautions in the application of the metacoupling framework. Strengthening the assessment of ecosystem services with the metacoupling framework can yield important insights toward sustaining ecosystem service provisions, balancing trade, offs, promoting regional and global cooperation, and achieving the United Nation’s Sustainable Development Goals.

Introduction

Ecosystem services are the benefits that people obtain from ecosystems. They are co-produced by interactions between ecosystems and human societies (Costanza et al., 1997; Daily, 1997; Mandle et al., 2021). To understand the impacts of such benefits and co-production on ecosystems, the assessment of ecosystem services has received widespread recognition from the scientific community and political decision-makers over the past decades (Fu et al., 2013; Mandle et al., 2021).

Ecosystem services function as links between ecosystems and human societies (Grunewald and Bastian, 2015). Such links are bi-directional, and include the supply of ecosystem services (the total amount of ecosystem services products provided within a specific area and seen as the upper limit of nature’s carrying capacity for human activities) and the demand for these services (ecosystem service products consumed or utilized within a specific area) (Grunewald and Bastian, 2015). To comprehensively understand the links between the supply and demand of ecosystem services, the framework of coupled human and natural systems (CHANS) has been proposed (Figure 1). The CHANS framework integrates patterns and processes that connect humans (different sectors and stakeholders) and natural systems (different abiotic and biotic factors) within and across multiple organization levels.

Figure 1.

Schematic representation of a coupled human and natural system.

In the Anthropocene era, human societies are becoming heavily reliant on the ecosystem supply, thus creating challenges for ecosystem services (e.g., habitat degradation, biodiversity loss). Adoption of the CHANS framework is particularly useful in addressing such complex challenges. For example, biodiversity is commonly considered to be somewhat shielded from human activity after an area is designated as a protected area. However, based on the CHANS framework, ecological degradation has been detected in the Wolong Nature Reserve, a protected area for giant pandas in southwestern China (Liu et al., 2001). The major driving force of such degradation is the increase in household numbers in the reserve, because more young people have established new households and no longer staying with their parents. Newly established households require construction materials (wood) and involve a variety of economic activities (e.g., agriculture, fuelwood collection, timber harvesting, road construction and maintenance, and herbal collection), leading to deforestation in the reserve and degradation of protected areas. The CHANS framework has been widely incorporated into habitat restoration and conservation endeavors in the Wolong Nature Reserve. Moreover, it has been quite successful because giant pandas have been downgraded from endangered to vulnerable levels (Xu et al., 2017). CHANS framework-based studies on ecosystem services have yielded fruitful scientific discoveries and useful policies over the past few decades, with most focusing on a specific place or simple comparisons between just a few different places (Alberti et al., 2011; Kramer et al., 2017).

Driven by intensive globalization, more human and natural interactions are occurring between geographically, culturally, and institutionally distant systems, and across local, regional, national, and global scales. Thus, moving from scattered and separate place-based research to systematically integrated research is becoming an urgent necessity. It is crucial to build a networked research scheme, promoting the assessment of ecosystem services, and generating novel insights for understanding complex relationships among the 17 United Nations Sustainable Development Goals (SDGs) within and between adjacent and distant places.

From CHANS to metacoupling

Place-based CHANS around the world are becoming increasingly connected through distant interactions, such as international trade, migration, cultural communication, and species invasion (Liu et al., 2007, 2021). This distant connectedness has profound implications for addressing global challenges, such as food security, energy security, biodiversity conservation, environmental protection, and human well-being (Sun et al., 2017; Tong et al., 2017; Tromboni et al., 2021). Therefore, it is becoming a major concern in the assessment of ecosystem services (Elmqvist et al., 2013; Grunewald and Bastian, 2015).

To address the distant connectedness among multiple CHANS, an umbrella concept, telecoupling, has been created, which refers to socio-economic and environmental interactions over distances (Liu et al., 2013; Sun et al., 2020). The telecoupling framework has been proposed to study these distant interactions; it consists of multiple CHANS and can be classified as a sending system, receiving system, and spillover system (Figure 2). Telecoupling has been widely applied in the assessment of ecosystem services (Liu et al., 2016) and in many other arenas (Hull and Liu, 2018; Rulli et al., 2019). According to recent reviews, the numbers of applications, publications, and citations on telecoupling are increasing since the release of the first telecoupling paper by Liu et al in 2013 (Kapsar et al., 2019; Sun et al., 2020).

Figure 2.

Schematic representation of the telecoupling framework.

However, the cumulative empirical studies show that the telecoupling framework and other frameworks have not explicitly integrated the interaction between adjacent CHANS (Liu, 2017). Although a collection of studies focuses on cross-border issues, such as transboundary air pollution (Abas et al., 2019) or socio-economic issues (e.g., migration and social remittances between Mexico and the USA) (Azizi and Yektansani, 2020), none of them examine socio-economic and environmental issues simultaneously.

The metacoupling framework has been proposed to integrate human and natural interactions within a system (intracoupling), between adjacent systems (pericoupling), and between distant systems (telecoupling) (Figure 3) (Liu, 2017, 2018). The framework has already been adopted in a range of studies, regarding watershed management (Merz et al., 2020), the diagnosis of inequity in cultivated land use (Chuai et al., 2021), the food-energy-water-CO₂ nexus in agricultural irrigation (Xu et al., 2020), and the fishery management (Carlson et al., 2020). Furthermore, some studies have already attempted to use the metacoupling framework in ecosystem services (Zhao et al., 2018).

Figure 3.

(a) Sketch of the metacoupling framework of a focal CHANS, an adjacent CHANS, and a distant CHANS, and their interrelationships (arrows). (b) Metacoupling includes intracoupling and intercoupling, while intercoupling includes pericoupling and telecoupling.

To demonstrate the utility of the metacoupling framework in the assessment of ecosystem services, I provide three related examples from China: Beijing’s water supply, soybean production and trade in northeastern China (the largest soybean production region), and banana plantation and displacement between China (southwestern China, the largest banana production region) and Laos (northern Laos) (Figure 4).

Figure 4.

Examples of the metacoupling framework in the assessment of ecosystem services.

Embracing the metacoupling framework in ecosystem services

Water supply and transfer

Beijing, China’s capital, is one of the most water-scarce cities in the world (119 m3·y−1 per capita, far below the international criterion of 1000 m3·y⁻¹ per capita), due to the overexploitation and pollution of water resources in recent decades (Wang et al., 2017; Ye et al., 2018).

Intracoupling. The water supply in Beijing is heavily affected by local interactsion between human and natural systems. First, the increase in population, which is currently around 20 million residents, and particularly, the increasing per capita water demand (e.g., for cooking, showering, and car washing), have aggravated water scarcity in the city (Yuan et al., 2014). Although the government has implemented a series of water-saving regulations, such as block-rate pricing, the effect is currently limited (Chen and Yang, 2009). Water pollution is another negative factor in the water supply. Many major rivers, such as the Yongding River, have been polluted and abandoned as sources of drinking water (Dai et al., 2020). Moreover, climate change has become a new threat. For instance, the historical average annual precipitation of Beijing ranges from 420 to 630 mm in most parts of the city, while meteorological data show that precipitation has been experiencing a decline at a rate of 4.96 mm/10a over the past decades (Song et al., 2014).

Pericoupling. Located in northern Beijing, Miyun Reservoir is the only surface water source for up to half of the domestic water in the city. However, competition between Hebei Province (upstream) and Beijing (downstream) for water resources originating in Hebei Province has intensified (Peisert and Sternfeld, 2005). Farmers living upstream of the Miyun Reservoir, Hebei Province, rely on water resources for agricultural and industrial activities, and Beijing’s demand for water continues to increase with its population growth. To address the water supply dilemma, a payment for ecosystem service program, the paddy land to dry land (PLDL) conversion program, was jointly proposed by Beijing and Hebei Province (Zheng et al., 2013). Beijing paid a certain amount of financial subsidies per year to farmers in the watershed of the Miyun Reservoir, Hebei Province, for land that was converted from rice to corn cultivation. The results show that both water quantity and quality in the Miyun Reservoir have been greatly improved because of the PLDL program. Furthermore, the PLDL program has secured and enhanced the water supply to Beijing (Xu et al., 2009; Zuo et al., 2011).

Telecoupling. Aiming to draw water from southern rivers to supply the dry north (including Beijing), the Chinese government initialized the South-North Water Transfer Project, a multi-decade infrastructure mega-project (Rogers et al., 2016; Xu et al., 2020). The central route of the project begins at the Danjiangkou Reservoir on the Han River, covering Xichuan County, Henan Province and Danjiangkou City, Hubei Province via the Grand Aqueduct and ultimately reaches Beijing. Such project has led to considerable socio-economic and environmental changes, including large-scale population resettlement (Rogers et al., 2020), and environmental impacts (Wilson et al., 2017). Thus, a comprehensive assessment of ecosystem services in the future will be required.

Soybean production and trade

Soybean production and trade are high-profile examples in CHANS and telecoupling studies (da Silva et al., 2021; Sun et al., 2018). Soybeans are an important food crop, providing oil and fodder. Although soybeans were originally domesticated by Chinese farmers, China has become the largest soybean importing country, because of its population growth and changes in dietary structure (from plant-based to meat-based) (Food and Agriculture Organization of the United Nations, 2021).

Intracoupling. Heilongjiang Province, located in northeastern China, is the largest soybean producing region, accounting for approximately one-third of the national soybean production (National Bureau of Statistics of China, 2021). Increased soybean imports (mainly from Brazil and the United States) and decreased soybean plantings in Heilongjiang from 2010 to 2015 have led to widespread changes in crop structure. Consequently, a conversion from soybean to corn crops occured in Heilongjiang Province, followed by a series of environmental problems (e.g., nitrogen pollution) (Sun et al., 2017, 2018).

Pericoupling. Burning crop residues is a common agricultural practice, although it has been banned or partially banned in many countries (Cao et al., 2008). Because the per-unit-weight dry matter of corn stalk is heavier than that of soybeans (Baghdadi et al., 2016), burning corn stalks produce more smog than burning soybeans. Changes in crop structure due to the conversion from soybeans to corn in Heilongjiang have led to more smog when burning stalks, largely worsening air conditions locally and nearby, particularly polluting in the neighboring country, Russia, via prevailing winds.

Telecoupling. Decreasing soybean production and increasing soybean demand have forced China to import more soybeans from Brazil, the United States, and other countries. Thus, the soybean trade has caused land use and land cover changes in many exporting countries (Macedo et al., 2012; Wright and Wimberly, 2013). For example, forest conservation in Brazil is facing greater pressure from soybean expansion, as the deforestation rate in the Amazon rainforest is now increasing at an unprecedented rate (Silva Junior et al., 2021).

Banana plantation and displacement

Southwestern China (Guangdong, Guangxi, and Yunnan provinces) is a traditional banana plantation region, accounting for more than 85% of the national total planted area (Ma et al., 2022, National Bureau of Statistics of China, 2021). Banana production is a pillar industry for local farmers.

Intracoupling. The spread of the plant disease, Fusarium Wilt Tropical Race 4, a soil-pathogenic fungus, has caused irreversible damage to the banana industry in southwestern China, leading to economic loss and ecological degradation (Friis and Nielsen, 2019; Zheng et al., 2018).

Pericoupling. The spread of this disease, coupled with a general depletion of soil quality in the banana-producing region of southwestern China, has led to the displacement of domestic banana plantations abroad, mainly in the neighboring country of Laos (northern part). Consequently, northern Laos (bordering part between the two countries) has experienced significant changes in land use and land cover, expressed as the extensive expansion of banana plantations and shrinkage of rice paddies.

Telecoupling. Traders that contract with local farmers in Laos for banana planting have exported bananas back to China, supplying consumers across the country.

Caveats in the application

Metacoupling identification. No single study can address all complex interactions between human and natural system; therefore, so it is essential to identify and integrate the most relevant and important interactions across multiple scales in the assessment of ecosystem services.

I suggest using the first law of geography, that is, distance decay, as one method to justify whether multiple CHANS connected by certain flow(s) are metacoupled. Distance decay means that the human and natural interactions involving locals decline as the distance between them increases, whereas metacoupled systems do not conform to this law. For example, although the distance between China and Brazil is approximately 16,622 km², soybean trade has significantly affected socio-economic and environmental systems in the two countries, such as changes in crop planting structure in China and deforestation in Brazil.

Spillover systems. Spillover systems in intracoupling, pericoupling, and telecoupling are the least studied and understood (Liu et al., 2018). For example, the displaced banana plantations from southwestern China to northern Laos can affect the banana trade from the Philippines to China, and new competition is likely to negatively affect farmers’ livelihoods in Laos and the Philippines (Friis and Nielsen, 2019).

Procedural regulations. Applications of the metacoupling framework, including the assessment of ecosystem services, should follow the operationalization steps proposed in the metacoupling paper by Liu et al in 2017 (Liu, 2017), which include (i) set research goals, objectives, questions, and hypotheses; (ii) define focal systems or systems of interest; (iii) review literature; (iv) identify intracoupling, pericoupling, and telecoupling; (v) study metacoupled components and their interrelationships; and (vi) after publishing the results in peer-reviewed journals and books, conduct communications, including presentations, academic discussions, and dissemination, via news and social media.

Perspectives

The Anthropocene era is full of uncertainties and surprises, including climate change, war, and COVID-19 pandemic, all of which have demonstrated the importance of assessing ecosystem services within intracoupling, between pericoupling and telecoupling. This is particularly true for the food supply in the ongoing Russia-Ukraine War. Direct effects of the war (intracoupling) include the suspension of food exports from Ukraine (the breadbasket of Europe), with future planting and harvest in question. The reduction of fertilizer exports from Russia (the largest nitrogen, second-largest potash, third-largest phosphatic fertilizer producing country) is also a concern. Far beyond the boundaries of Ukraine and Russia, the war has threatened global food security. Many European countries that rely on food crops from Ukraine to feed their people and fertilizers from Russia to feed their food crops (pericoupling) are struggling to find alternatives; and the rest of the world is experiencing spiked prices of agriculture commodities (telecoupling).

Adoption of the metacoupling framework in the assessment of ecosystem services is still at the start-up stage. Moreover, it is facing various challenges. Here, I list two challenges that must be addressed immediately. The first is quantification. To date, many papers focus on applications of the metacoupling framework conceptually, highlighting the importance of quantitative analysese. Many quantitative attempts have been made to assess ecosystem services in telecoupling studies using network analyses, GTAP modelling, and the telecoupling toolbox (Sonderegger et al., 2020; Tonini and Liu, 2017; Yao et al., 2018). Such studies shed light on quantitative metacoupling analyses. The second challenge involves platform. Since the concept and framework of metacoupling have been widely applied, it is necessary to build platforms (e.g., websites, forums) to regulate language usage (e.g., terminology), recommend application procedures, and organize sections in ecosystem-services meetings and conferences so as to promote an understanding and applications of the metacoupling framework in the assessment of ecological services.

The illustrations provided here indicate the powerfulness of metacoupling in the assessment of ecosystem services, such as helping identify knowledge gaps, advance ecosystem services, develop relevant policies, and reveal hidden and important interactions within a system (intracoupling), between adjacent systems (pericoupling), and between distant systems (telecoupling). Metacoupling also enhances the governance of ecosystem services. Future research in ecosystem services that embraces the metacoupling framework will add important insights toward sustaining provision, balancing tradeoffs, promoting regional and global cooperation, and advancing SDG goals.