Organic and conservation agriculture promote ecosystem multifunctionality


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Science Advances 20 Aug 2021:
Vol. 7, no. 34, eabg6995
DOI: 10.1126/sciadv.abg6995

Article

Abstract

Ecosystems provide multiple services to humans. However, agricultural systems are usually evaluated on their productivity and economic performance, and a systematic and quantitative assessment of the multifunctionality of agroecosystems including environmental services is missing. Using a long-term farming system experiment, we evaluated and compared the agronomic, economic, and ecological performance of the most widespread arable cropping systems in Europe: organic, conservation, and conventional agriculture. We analyzed 43 agroecosystem properties and determined overall agroecosystem multifunctionality. We show that organic and conservation agriculture promoted ecosystem multifunctionality, especially by enhancing regulating and supporting services, including biodiversity preservation, soil and water quality, and climate mitigation. In contrast, conventional cropping showed reduced multifunctionality but delivered highest yield. Organic production resulted in higher economic performance, thanks to higher product prices and additional support payments. Our results demonstrate that different cropping systems provide opposing services, enforcing the productivity–environmental protection dilemma for agroecosystem functioning.

INTRODUCTION

Global food production has more than doubled in the past 60 years. This has been achieved through land use change and use of mineral fertilizers, pesticides, breeding of new crop varieties, and other technologies of the “Green Revolution” (1, 2). However, increased use of agrochemicals, land conversion, farm expansion, and farm specialization have a negative impact on the environment and have caused habitat and biodiversity loss, pollution, and eutrophication of water bodies, increasing greenhouse gases emissions and reduced soil quality (1, 3, 4). Thus, one of the main challenges for the future of agriculture is to produce sufficient amounts of food with minimal environmental impact (1). However, to date, there is lack of appropriate methods and tools to evaluate, design, and track the multifunctionality and sustainability of agricultural production.

For agronomists, the focus of agricultural systems is dedicated to productivity, while ecologists and environmental researchers focus on the environmental impact of agriculture. Ideally, agricultural systems should provide the desired balance of provisioning services (e.g., food production), regulating services (e.g., soil, water, and climate protection), and supporting services (e.g., biodiversity and soil quality conservation) within viable socioeconomic boundaries (e.g., ensured income and suitable working conditions). However, systemic evaluations of the diverse services and trade-offs provided by different agricultural practices are scarce, and this has been viewed as a major research gap (5, 6).

In the past 15 years, there have been considerable efforts to conceptualize ecosystem services (ESs), defining their contribution to human well-being and bring it into policy and planning. Examples such as the Millennium Ecosystem Assessment (MEA) (7), The Economics of Ecosystems and Biodiversity (8), or the Intergovernmental Platform on Biodiversity and Ecosystem Service (9) are global initiatives that are integrated in national monitoring programs such as the U.K. National Ecosystem Assessment (UKNEA) framework (10). Even if these concepts and framework are increasingly recognized, there is a lack of implementation in practice due to difficulties to appropriately measure and value ES and to institutionalize outcomes (11).

One of the key approaches to measure and appropriately manage agroecosystems is to gain a solid understanding of how farming practices influence a wide range of ecosystem functions and services and to summarize these effects in a meaningful way (12, 13). The “ability of ecosystems to simultaneously provide multiple functions and services” can be assessed by calculating ecosystem multifunctionality (EMF), an approach widely used in ecology (14, 15). Here, we define ecosystem functions as the biotic and abiotic processes that make up or contribute to ESs either directly or indirectly.

A range of studies has assessed how different drivers including biodiversity and land use intensity affect individual functions and EMF (16–19). However, this approach is still poorly developed for agroecosystems (15), where anthropogenic management plays a key role in determining ecosystem functioning (i.e., specific crop management practices like tillage intensity and chemical and organic input sources and amounts). Moreover, the number of ecosystem functions used to assess EMF varies greatly among studies, and there is often little explanation of why certain variables are included (15). Thus, a next frontier is to investigate how major cropping systems (e.g., conventional, organic, and conservation agriculture) influence different ecosystem functions and EMF and embed such analyses in a broader conceptual ES framework supporting producer and policy decisions.

The main objective of this study is to assess the overall performance of important cropping systems within an adapted ES framework using the EMF methodology applied in ecology. To do this, we use a 6-year dataset from the long-term FArming System and Tillage (FAST) experiment (fig. S1) where we compare the agronomical, ecological, and economic impacts of four arable cropping systems [conventional intensive tillage (C-IT), conventional no tillage (C-NT), organic intensive tillage (O-IT), and organic reduced tillage (O-RT); see Materials and Methods and tables S1 to S3 for detailed management description]. We focus on these specific management strategies since conservation and organic agriculture are two main alternatives to conventional management and are often promoted as more environmentally friendly practices. Organic agriculture prohibits the use of synthetic inputs (e.g., pesticides and fertilizers), and a range of studies show that organic farming enhances biodiversity and reduces environmental impacts but results in lower productivity (4, 5, 20, 21). Conservation agriculture, in turn, is based on three main pillars: minimum mechanical soil disturbance, permanent soil cover, and species diversification, which are applicable in many different farming contexts (22). Several studies indicate that conservation agriculture has positive effects on soil quality and protection, water regulation, energy use, and production costs (23), but productivity increases are minimal or even negative (24) and often dependent on herbicide use (25). In our study, C-NT and O-RT systems are considered to reflect conservation agriculture as the three defined pillars of conservation agriculture are largely fulfilled (minimum tillage, 6-year crop rotation, and permanent soil cover with crop residues and cover crops).

We assessed 43 variables in each cropping system, from which 38 were classified into nine agroecosystem goods and four ecosystem categories using an adapted ES framework and five were used as agronomic co-variables. We based our classification on the MEA and UKNEA frameworks (7, 10) and grouped our variables into proxies for ecosystem functions representing ecosystem processes and services and we finally valued them as ecosystem goods. Ecosystem functions, services, and goods were attributed to supporting, regulating, and provisioning ES categories. In addition, we added socioeconomic proxies and an economic category to the classical ES framework (Fig. 1 and tables S4 and S5). We did this because agroecosystems also have a socioeconomic dimension for producers and policy makers. The following nine final agroecosystem goods were used for multifunctionality assessments: biodiversity conservation, soil health preservation, erosion control, water and air pollution control, food production, income, work efficiency, and financial autonomy.

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