Implications of agricultural transitions and urbanization for ecosystem services

Abstract

Historically, farmers and hunter-gatherers relied directly on ecosystem services, which they both exploited and enjoyed. Urban populations still rely on ecosystems, but prioritize non-ecosystem services (socioeconomic). Population growth and densification increase the scale and change the nature of both ecosystem- and non-ecosystem-service supply and demand, weakening direct feedbacks between ecosystems and societies and potentially pushing social–ecological systems into traps that can lead to collapse. The interacting and mutually reinforcing processes of technological change, population growth and urbanization contribute to over-exploitation of ecosystems through complex feedbacks that have important implications for sustainable resource use. In this transition, as the population grows, the red loop overwhelms the green loop to become the dominant regime driving the use of ecosystem goods and services (ESS). a, In the starting green loop, rural populations manage their local ecosystems. b, As the population grows, a 'shadow' red loop begins to develop; changes in socioeconomic variables, such as increased demand for food, fibre and fuel, lead to greater local ecosystem impacts. c, The red loop gains prominence as demand for services shifts from a need for ecosystem services to a need for non-ecosystem services. d, As the demand for services shifts, the red loop becomes the dominant driver in the flow of ecosystem services and is accompanied by an upscaling and specialization process that results in the gradual alienation of urban people from the ecosystem; the strength of the connection between the local ecosystem and society is heavily reduced (dashed line). This can easily result in over-exploitation of ecosystems and ecological degradation. Full size image View in article Basic household needs create a local demand for ecosystem goods and services (ESS). This may be expressed as direct and unregulated impacts on ecosystems, or, more typically, as 'use actions' (consumptive and non-consumptive) that are governed by rules, laws, policies and customs (institutions). Among use actions, those that have the highest ecological impacts are generally those that involve direct extraction of resources (for example, logging, cultivation or water extraction). Use actions affect the provision of ESS as well as 'disservices' (pathogens, crop damage or floods). The degree to which human needs are met by ecosystem services then affects future demand, completing the loop. The direct interactions of people and ecosystems are gradually overrun by the red loop, in which the focus is non-ESS, despite the continued importance of ecosystems for the community. Ongoing local and regional impacts on ecosystems are hidden from urban dwellers by outsourcing and infrastructure development. The two 'wild card' variables (in grey), human health and regional processes, may be present in either red- or green-loop situations and may create ecological or socioeconomic surprises that can alter system dynamics. Full size image View in article A typical development trajectory from an agricultural (green loop) to industrial (red loop) society involves individual households gaining wealth while some level of ecosystem degradation occurs. Depending on population growth rates and governance, societies may grow without true socioeconomic restructuring (green trap) or become rich and continue to over-exploit ecosystems (red trap). The dashed lines indicate avoidable transitions. Both traps can lead to socioeconomic collapse. One of the primary challenges of development and policy initiatives is to shift societies from a green trap to a red loop (dotted line) without heavily altering consumption patterns, thus maintaining a relatively high individual quality of life without entering a red trap. Full size image View in article Cereal data illustrate the failed transition from a green to a red loop, and the resulting entry into a green trap. Cereal yield per hectare (a) has declined and the large expansion of the cultivated area (b) is primarily responsible for the increase in total cereal production (c), despite an overall increase in fertilizer use (d). Cereal production per 1,000 people (e) dropped slightly as the human population grew (f). This would have led to a decline in cereal availability per capita. However, since the 1990s, extensive cereal imports (g) have compensated for the shortfall, with the linked collapse of cereal exports (h). Full size image View in article