Compendium Vol. 3 No. 1: Ecological intensification

The concept of ecological intensification in agriculture offers a framework for handling the question of how to produce enough food for a growing global human population while simultaneously protecting biodiversity. It draws on the language of ecosystem services, which includes supporting services such as soil formation, regulating services (pollination and pest control), provisioning services (production of a consumable good) and cultural services (educational and recreational) tendered by nature upon which humans depend.

Despite being anthropocentric simplification the complex web of relationships that make up an ecosystem, the concept of ecosystem services is useful in drawing attention to humanity’s reliance on nature. In the context of agriculture, recognizing the processes (especially soil creation, habitat structure, nutrient mobilization through microbe-plant symbioses, and pollination) that undergird crop health, growth and yield can enable farmers to design farming systems that meet agronomic objectives while restoring ecosystem function to cropland.  

Farmers can activate certain elements of ecosystem function according to the specific problems and opportunities they see on their farmland. For example, Martin et al. [2019] explain that simply maximizing the amount of edge around cropland (for example, with smaller fields) boosts pollinator and pest predator activity in crop fields, thereby increasing yield. Similarly, increasing soil organic matter reduces the need for fertilizer, thereby reducing pressure from pests such as aphids that proliferate on nitrogen fertilized crops, and thus also reducing the need for pesticides [Garratt 2018]. Furthermore, weed colonization of cropland can potentially limit insect and pathogenic infestations [Muneret 2018].

Scenarios for meeting global food demand through ecological intensification of agriculture focus on closing yield gaps through a combination of methods in countries with low rates of agricultural productivity and higher rates of food insecurity, while maintaining yields in already high-yielding countries through a transition to ecological practices. This way, more food is produced in the places where it is most needed and in a way that minimizes (and potentially even halts) biodiversity loss. In the meantime, agricultural productivity is maintained through a transition to ecological practices in already high-yielding contexts.

The greatest contribution to humanity from the most productive and industrialized areas of the world would be to maintain current productivity using less inputs of non-renewable resources and reducing their huge environmental impact; in other words, producing ‘the same with less’ [Tittonell 2016: 23].

The greatest contribution to humanity from the most productive and industrialized areas of the world would be to maintain current productivity using less inputs of non-renewable resources and reducing their huge environmental impact; in other words, producing ‘the same with less’ [Tittonell 2016: 23].

To clarify the premises of ecological intensification, one can examine a contrasting approach to increasing global crop yield while minimizing biodiversity loss (its name, “sustainable intensification,” is similar to “ecological intensification,” and may confuse matters somewhat). An underlying premise of sustainable intensification is that increasing both agricultural yield and wildlife habitat in a particular place and time are mutually exclusive objectives.

Eschewing the viability of agricultural extensification (expanding the amount of land dedicated to agriculture), given well-known environmental problems associated with conversion of wild or semi-wild land to cropland, Egli et al. [2019] argue for increasing yields on existing farmland. The authors presume an inherent conflict between biodiversity preservation and agricultural intensification, however, where the latter is deemed achievable only through the high input methods that dramatically boosted yields in the 20th Century while also eroding biodiversity.

High input agriculture negatively affects multiple taxa and multiple dimensions of biodiversity, in particular farmland species. These negative effects have mostly been attributed to habitat simplification, inputs of fertilizer, pesticides, and irrigation.

Despite such externalities, the authors remain optimistic about future yield increases through industrial practices.

Past trends and future projections suggest large production increases through intensification on existing croplands. Yield increases contributed three quarters of the agricultural production gains between 1985 and 2005, and were mainly achieved through enhanced fertilization, irrigation and pest control, shortening of crop rotations and fallow periods, mechanization, and planting of improved crop varieties [Egli 2019: 2].

The authors introduce the possibility, therefore, of global land-use optimization: countries whose biodiversity-loss potential from agricultural intensification is lower (such as in Eastern Europe, Russia and North America) should maximize agricultural production. This would increase the global food supply enough that agricultural production could be reduced in global hotspots of biodiversity, thereby protecting biodiversity where it is the richest.

There are several problems with this strategy. As the authors themselves note, it would result in reduced agricultural output in high-biodiversity countries with an already lower level of food security and higher economic dependencies on the agricultural sector. In addition, further concentration of food production would deepen reliance on a global food system subject to international market volatility and relying on emissions-heavy long-distance shipping. Moreover, this study assumes yield on existing cropland can still increase to reach 80% of its potential, despite that yield growth from industrial innovation has already stagnated and the mineral resources that drive these techniques are dwindling. Furthermore, flooding, heat waves and droughts occurring with ever greater frequency will particularly stress crops growing in conditions of monoculture and damaged soils.

Lastly, the authors neglect to account for the potential of urban agriculture and forest food farming to increase agricultural production without converting wildlands, and, more generally, the possibility that agroecological practices are capable of increasing or maintaining yield in the process of restoring ecosystem function.

When all you have is a hammer, everything looks like a nail. For more than 50 years, the Green Revolution approach to farming has been our hammer, making weeds and insects look uniformly like nails, to stretch a metaphor. We’ve been taught to treat every other living thing growing among the crops in our fields (or yards or gardens) as the enemy, while ecological intensification teaches us to understand the interdependent relationships between different species growing together. It calls on us to search out the ways our crops benefit from the presence of various species in their midst (including the microorganisms we cannot even see), and to optimize those synergies in the skilled expression of our craft as farmers (or gardeners).

Compilation of article summaries on ecological intensification

Ecological intensification: local innovation to address global challenges, Tittonell et al. 2016

World agriculture cumulatively produces enough to feed the whole human population and more, yet hundreds of millions of people on the planet are hungry due to problems of access to food. Noting that agricultural productivity is unevenly distributed around the globe, this book chapter proposes food security through ecological intensification in areas with low productivity and higher rates of hunger. This strategy runs counter to a dominant narrative that agricultural productivity even in high-input, high-yielding farming systems in industrialized countries should increase to fight world hunger. Rather, these authors posit, developed countries should adopt ecological intensification to maintain existing high levels of productivity by replacing synthetic and high-tech inputs with practices enlisting ecosystem services.

In the most productive and industrialised areas of the world the concept of ‘more with less’ is certainly engaging but rather utopic, as these agricultural systems operate mostly beyond their physical and economic efficiencies already. It is hard to get ‘more’ from these systems and this should not be a priority from a global food security perspective, as such production does not contribute to alleviate hunger in the poorest regions of the world. The greatest contribution to humanity from the most productive and industrialised areas of the world would be to maintain current productivity using less inputs of non-renewable resources and reducing their huge environmental impact; in other words, producing “the same with less” [Tittonell 2016: 23].

To illustrate the point that best practices are context specific, the authors describe a variety of approaches to ecological intensification undertaken in various parts of the world. In Uruguay, ranchers help preserve ecologically important, biodiverse grasslands by changing their grazing practices to enhance pasture and livestock productivity with no external inputs. In addition to revitalizing the grasslands, ranchers increased their incomes, allowing them to stay in business and preserve the grassland rather than selling it for conversion to crop production.

In Ethiopia, wheat productivity improves when grown under the canopy of Faidherbia albida, a prevalent local tree, which provides shade at critical moments of wheat development, increases moisture availability, and decreases the incidence of disease. “These benefits were found to result in wheat producing 23% more grain and 24% more straw under the canopy of F. albida compared to sole wheat [Tittonell 2016: 12].”

The analysis of agricultural production systems that reproduce the ecological structure of the native savannah in the Ethiopian highlands showed that biodiversity should not only be seen as a ‘service’ from farming landscapes but rather as the basis for their functioning [Tittonell 2016: 22].

The authors call for the anchoring of ecological intensification of agriculture into social, cultural and policy structures. This could be done through local innovation, policy supporting such innovation, and through multi-stakeholder platforms for dialogue bringing together researchers, local, niche innovators, and actors representing the dominant food system.

Options for the ecological intensification of agriculture can be inspired by the type of interactions between structures and functions that can be observed in nature, by the practical experience of local indigenous knowledge, and by combining these with the latest scientific knowledge and technologies. Ecological intensification calls for a constant dialogue between the practical wisdom of farmers and our own scientific wisdom [Tittonell 2016: 25].

To accelerate change, grassroots movements should seek to influence policy toward acknowledging “diversity in development directions for the agricultural sector” [Tittonell 2016: 20].  

Thus, as the private sector will continue to invest in patentable technologies – understandably – to reinforce their position in the current socio-technical regime, the key role of the public sector should be to reinforce the diversity of approaches, prioritizing alternative rather than mainstream technologies, creating favorable ‘openings’ in established socio-technical regimes, and embracing the complexity and the associated transaction costs of system innovation programs or what could be called ‘co-innovation systems’. In other words, investing in the creation and support of new niches rather than supporting technological ‘solutions’ that are already embedded in current regimes [Tittonell 2016: 25].      

Ecological intensification: harnessing ecosystem services for food security, Bommarco et al. 2013

This review examines the concept of ecological intensification as a way to increase global food production by enhancing the ecological functionality of farmland.

We present ecological intensification as an alternative approach for mainstream agriculture to meet [future climatic, economic and social] challenges. Ecological intensification aims to match or augment yield levels while minimizing negative impacts on the environment and ensuing negative feedbacks on agricultural productivity, by integrating the management of ecosystem services delivered by biodiversity into crop production systems [Bommarco 2013: 230].

The idea of ecological intensification stems from the concept of ecosystem services, which refers to the benefits humans derive from ecosystems. These services are grouped into four types: supporting (such as soil formation by microorganisms), regulating (such as pest control, crop pollination, climate regulation and water purification), provisioning (such as food, fiber, fuel and water) and cultural (such as education, recreation and aesthetic).

Ecological intensification is based on managing service-providing organisms that make a quantifiable direct or indirect contribution to agricultural production [Bommarco 2013: 230].

The authors specify that: “crop yield has been defined as a provisioning ecosystem service, but the yield that is harvested in a given location depends largely on several supporting and regulating services” [Bommarco 2013: 231], such as soil production and pollination. And they note that these supporting and regulating ecosystem services underpin all agricultural production, including high-input industrial systems. For example, no matter how healthy and productive a crop is, yield will suffer if it’s not well pollinated, an observation consistent with Liebig’s Law of the Minimum. “One or several of these services can limit production and, even if all other services are optimized, no or little additional output will be attained until this ecosystem service shortfall is addressed” [Bommarco 2013: 231].

Beyond fulfilling a simple mechanistic role as a medium for crops to root into, soils provide multiple ecosystem services that support crop growth.

Soil services that promote plant growth include pest and disease regulation, nutrient flow, and soil formation and structure that allow for root penetration, gas exchange, water retention, and erosion control. These processes are mediated by an immense, diverse, and largely unexplored biological community of mainly bacteria and fungi, but also protozoa, nematodes, arthropods, and earthworms [Bommarco 2013: 232].

Soil services that promote plant growth include pest and disease regulation, nutrient flow, and soil formation and structure that allow for root penetration, gas exchange, water retention, and erosion control. These processes are mediated by an immense, diverse, and largely unexplored biological community of mainly bacteria and fungi, but also protozoa, nematodes, arthropods, and earthworms [Bommarco 2013: 232].

The management practices required to activate and optimize these soil services involve increasing soil organic matter (SOM) and diversifying crop rotation.

Ecosystems also provide the regulating services of biological pest control and crop pollination. Natural pest control can enhance or maintain yield even in pesticide-based production systems. However, the overuse of pesticides can severely damage ecosystem-based pest regulation, leading to pest resurgence or crop production system collapse. Strategies to enhance pest-predator populations “include landscape-level diversification by creation or conservation of natural and resource-rich habitat, combined with directed or diversified crop rotation and decreased pesticide pressure” [Bommarco 2013: 234]. Similarly, “pollinators can be promoted at the field or farm scale by enhancing floral resources and nesting sites, thereby potentially reducing the part of the yield gap caused by pollination deficits” [Bommarco 2013: 234].

In conclusion, the authors recommend that ecological intensification strategies increasingly replace conventional, industrial practices in developed countries, where the average yield potential has largely already been met, while using ecological intensification in combination with conventional strategies to close the yield gap in parts of the world where yields are low.

Evidence that organic farming promotes pest control, Muneret et al. 2018

Citing the problems posed globally by pesticide use and farmland expansion, this study looks at the potential of organic farming, seen as a popular prototype of ecological intensification, to limit pest infestations. Ecological intensification “is based on optimizing the ecological functions that support ecosystem services to increase the productivity of agro-ecosystems” [Muneret 2018: 361], and thus serves as a framework for evaluating farming system changes that could handle both ecological stress/collapse and human population growth. “Organic farming is a certified production system based on the principle of using farming practices that are expected to enhance ecological processes while prohibiting the use of external synthetic inputs” [Muneret 2018: 361].

Our findings in particular show that organic farming practices are able to match or outperform conventional pest control practices against pathogens and animal pests [such as insects] whereas weeds are much more abundant in organic than in conventional systems. Thus, ecological intensification based on organic farming can contribute to the control of animal pests and pathogens by enhancing biological control services and limiting their infestation levels [Muneret 2018: 365].

Whereas conventional pest control emphasizes top-down control with pesticide, ecological pest control is achieved through multiple processes:

Once established, pest populations within agro-ecosystems are affected, to varying degrees, by three ecological processes: bottom-up effects mediated by soil or plant communities involving, for instance, plant quality or habitat structure, horizontal processes within a given trophic level such as competition for resources between individuals or populations, and top-down control by natural antagonists such as predation or parasitism [Muneret 2018: 363].

Given the benefits of biodiversity for enhancing these three ecological effects, the authors explain that weeds, which are not as well suppressed in organic systems, may actually be beneficial in terms of limiting infestation by animals/insects and pathogens.

Our analysis shows that organic farming results in much higher weed infestation. This result is supported by previous studies that have shown higher abundance and diversity of plant communities within organic arable fields. We assume that this higher weed infestation, in turn, most likely influences animal pest and pathogen populations. These bottom-up effects of plant communities on higher trophic levels have been demonstrated and more abundant or diverse plant communities have been found to limit insect and disease infestation through direct and indirect mechanisms because of higher structural complexity or lower habitat quality under increased plant diversity. Although this needs further investigation, the observed performance of organic farming on animal pest and pathogen infestation may result from bottom-up effects generated by the higher weed infestation levels in organic cropping systems [Muneret 2018: 364].

Although the authors didn’t examine the effects of pest infestations on yield, they note that previous studies have suggested that weeds do not necessarily result in crop yield reductions in organic systems.

Although this needs further investigation, the observed performance of organic farming on animal pest and pathogen infestation may result from bottom-up effects generated by the higher weed infestation levels in organic cropping systems [Muneret 2018: 364].

The interplay of landscape composition and configuration: new pathways to manage functional biodiversity and agroecosystem services across Europe, Martin et al. 2019

This paper analyzes 49 studies (1515 landscapes encompassing both organic and conventional agricultural production) in Europe to determine “effects of landscape composition (% habitats) and configuration (edge density) on arthropods^[7] in fields and their margins, pest control, pollination and yield” [Martin 2019: 1].

Edge density is measured as the length of edge per area of land. Edges between adjacent crop fields and between crop fields and semi-natural areas such as grasslands or other land patches not used for crops allow for “exchange between landscape patches” [Martin 2019: 4] for pollinators, pest predators and other providers of ecosystem services. High edge density is associated with smaller field size, and lower edge density with larger field size.

Complex landscapes where small and/or irregularly shaped fields and habitat patches prevail have a high density of edges. Due to increased opportunities for exchange, these landscapes are likely to support spillover of dispersal-limited populations between patches [Martin 2019: 3].

Researchers found that:

In landscapes with high edge density, 70% of pollinator and 44% of natural enemy species reached highest abundances and pollination and pest control improved 1.7- and 1.4-fold, respectively. Arable-dominated landscapes with high edge densities achieved high yields. This suggests that enhancing edge density in European agroecosystems can promote functional biodiversity and yield-enhancing ecosystem services [Martin 2019: 1].

Just as high edge density is shown here to maintain yield, low edge density, especially when combined with a lower amount of surrounding semi-natural habitat, can reduce yield.

Reduced pollination and pest control at low edge density may have been compensated by external inputs in productive landscapes. … Intermediate to low yields in landscapes with high % arable, low % semi-natural habitat and low edge density may underpin the risks of ongoing conventional intensification resulting in yield stagnation or reduction despite high agricultural inputs [Martin 2019: 9].

This article illustrates the important role of ecosystem services in maintaining crop yield, as well as the relatively simple management decisions farmers can make to enhance the habitat of arthropods providing those services.