There is worldwide concern about the environmental costs of conventional intensification of agriculture. Growing evidence suggests that ecological intensification of mainstream farming can safeguard ...food production, with accompanying environmental benefits; however, the approach is rarely adopted by farmers. Our review of the evidence for replacing external inputs with ecosystem services shows that scientists tend to focus on processes (e.g., pollination) rather than outcomes (e.g., profits), and express benefits at spatio-temporal scales that are not always relevant to farmers. This results in mismatches in perceived benefits of ecological intensification between scientists and farmers, which hinders its uptake. We provide recommendations for overcoming these mismatches and highlight important additional factors driving uptake of nature-based management practices, such as social acceptability of farming.
Ecological intensification aims to harness ecosystem services to sustain agricultural production while minimising adverse effects on the environment.
Ecological intensification is championed by scientists as a nature-based alternative to high-input agriculture but meets with little interest from growers.
Scientific evidence underlying ecological intensification is often unconvincing to growers, as it is based on small-scale studies of ecological processes unlinked from agricultural production.
Grower interest can be enhanced by evidence of the agronomic and economic benefits most relevant to farmers and measured at the scales of operation of farm enterprises.
In addition to concrete benefits, concerns of the general public about adverse effects of industrial farming can promote adoption of ecological intensification, both directly and indirectly, by enhancing political will to use regulatory instruments.
There is increasing recognition that pollination deficits are limiting crop yields world‐wide. However, management strategies for optimal insect pollination are still unclear for most crops. Current ...management focuses on providing high densities of honeybees, but recommended densities are highly variable, even within single crops and cultivars.
We performed an extensive literature search to record honeybee densities (colony density and/or flower visitation rates) and crop productivity (fruit set, seed set, fruit weight and/or yield). Effect sizes were represented as the difference in crop productivity between the two most extreme levels of honeybee densities.
Out of 795 reviewed studies, only 22 analysed the effect of at least two levels of honeybee densities on crop productivity (reporting 60 resulting effect sizes in total). Moreover, few recommendations for crop pollination management are based on results from controlled experimental designs, and with comparable methodology.
We found that both colony density and visitation rates increased all the productivity variables. However, effects were nonlinear for visitation rates, suggesting that there is an optimum (mean of 8–10 visits per flower) beyond which more honeybees are not beneficial (and can even be detrimental) for crop productivity.
Effect sizes for visitation rates were greater than that for colony densities, suggesting that visitation rates are a more direct measure of the pollination process. Data on the relation between colony density and visitation rates are lacking. Interestingly, effect sizes for visitation rates were greater for crops with separate sexes than those with hermaphroditic flowers; therefore, the benefits of honeybee pollination vary according to the crop biology.
Synthesis and applications. Current practices for crop pollination assume that more honeybees are always better for crop yield, even if the effect of this management on crop production still unclear. In contrast, our analyses suggest that there is an optimum for honeybee densities. Despite the importance of honeybees and pollinator‐dependent crops world‐wide, there is a lack of studies designed for finding such an optimal level of crop pollination. Our analyses further suggest that visitation rates could be used as a proxy to guide management recommendations such as colony density and spatial arrangement.
Foreign Language Resumen
Los déficits de polinización están limitando la productividad de los cultivos en todo el mundo. Para sustentar el servicio de polinización en zonas de agricultura intensiva, el manejo actual consiste en saturar los cultivos de flores con abejas melíferas proveyendo altas densidades de colmenas. Sin embargo, se sabe muy poco sobre la eficiencia de este manejo para poder alcanzar una polinización óptima y existe controversia respecto las densidades recomendadas.
Realizamos una síntesis global de la literatura científica para registrar la densidad de abejas meliferas (tasa de visitas o densidad de colmenas) y la productividad de los cultivos (cantidad de frutos o de semillas por flor, peso del fruto, o rendimiento por hectárea o planta). Los tamaños de efecto se calcularon como la diferencia en la productividad entre los dos niveles más extremos de densidades de abejas.
De los 795 estudios revisados, solo 22 analizaron el efecto de al menos dos niveles de densidad de abejas sobre la productividad de los cultivos (resultando en 60 tamaños de efecto en total). Además, pocos estudios se basan en los resultados de diseños experimentales controlados y con una metodología comparable.
Encontramos que tanto la tasa de visita como la densidad de colmenas aumentaron todas las variables de productividad. Sin embargo, el efecto de la tasa de visita fue curvilíneo, lo que sugiere que hay un óptimo (8‐10 visitas por flor) más allá del cual mas abejas no es beneficioso (o incluso perjudicial) para la productividad de los cultivos.
Los tamaños de efecto para la tasa de visitas fueron mayores que para la densidad de colmenas, lo que sugiere que la tasa de visitas es una medida más directa del proceso de polinización. Faltan datos sobre la relación entre la tasa de visitas y la densidad de colmenas. De modo interesante, el tamaño de efecto de la tasa de visitas fue mayor para cultivos con sexos separados que para aquellos con flores hermafroditas, lo que sugiere que los beneficios de la polinización por la abeja melífera dependen de la biología floral.
Síntesis y aplicaciones. El manejo actual para la polinización de los cultivos asume que más abejas siempre aumenta la productividad de los cultivos. En cambio, nuestros análisis sugieren que existe un óptimo para la tasa de visita de abejas y que esa variable podría usarse como un proxy para guiar las recomendaciones de manejo, como la densidad de colmenas y su disposición espacial.
Current practices for crop pollination assume that more honeybees are always better for crop yield, even if the effect of this management on crop production still unclear. In contrast, our analyses suggest that there is an optimum for honeybee densities. Despite the importance of honeybees and pollinator‐dependent crops world‐wide, there is a lack of studies designed for finding such an optimal level of crop pollination. Our analyses further suggest that visitation rates could be used as a proxy to guide management recommendations such as colony density and spatial arrangement.
Scientists and policy-makers globally are calling for alternative approaches to conventional intensification of agriculture that enhance ecosystem services provided by biodiversity. The evidence ...reviewed here suggests that alternative approaches can achieve high crop yields and profits, but the performance of other socioeconomic indicators (as well as long-term trends) is surprisingly poorly documented. Consequently, the implementation of conventional intensification and the discussion of alternative approaches are not based on quantitative evidence of their simultaneous ecological and socioeconomic impacts across the globe. To close this knowledge gap, we propose a participatory assessment framework. Given the impacts of conventional intensification on biodiversity loss and greenhouse gas emissions, such evidence is urgently needed to direct science-policy initiatives, such as the United Nations (UN) 2030 Agenda for Sustainable Development.
Concerns regarding the ecological footprint of conventionally intensified agriculture are global.
Alternative, more sustainable farming systems must also perform well in both social and economic terms.
The evidence reviewed shows that alternative farming systems can achieve high yields and profits.
However, most studies analyze only one dimension of performance, usually the ecological.
The study of each dimension belongs to different research fields, each with its own idiosyncrasies and vocabulary.
A common experimental and multidimensional framework allows for a participatory assessment of alternative approaches to conventional intensification.
Such assessment can support farmers and policy-makers to achieve greater sustainability.
The global increase in the proportion of land cultivated with pollinator‐dependent crops implies increased reliance on pollination services. Yet agricultural practices themselves can profoundly ...affect pollinator supply and pollination. Extensive monocultures are associated with a limited pollinator supply and reduced pollination, whereas agricultural diversification can enhance both. Therefore, areas where agricultural diversity has increased, or at least been maintained, may better sustain high and more stable productivity of pollinator‐dependent crops. Given that >80% of all crops depend, to varying extents, on insect pollination, a global increase in agricultural pollinator dependence over recent decades might have led to a concomitant increase in agricultural diversification. We evaluated whether an increase in the area of pollinator‐dependent crops has indeed been associated with an increase in agricultural diversity, measured here as crop diversity, at the global, regional, and country scales for the period 1961–2016. Globally, results show a relatively weak and decelerating rise in agricultural diversity over time that was largely decoupled from the strong and continually increasing trend in agricultural dependency on pollinators. At regional and country levels, there was no consistent relationship between temporal changes in pollinator dependence and crop diversification. Instead, our results show heterogeneous responses in which increasing pollinator dependence for some countries and regions has been associated with either an increase or a decrease in agricultural diversity. Particularly worrisome is a rapid expansion of pollinator‐dependent oilseed crops in several countries of the Americas and Asia that has resulted in a decrease in agricultural diversity. In these regions, reliance on pollinators is increasing, yet agricultural practices that undermine pollination services are expanding. Our analysis has thereby identified world regions of particular concern where environmentally damaging practices associated with large‐scale, industrial agriculture threaten key ecosystem services that underlie productivity, in addition to other benefits provided by biodiversity.
Increasing cultivation of pollinator‐dependent crops has placed a stress on global pollination capacity, which could have been ameliorated by a concomitant increase in agricultural diversification. However, this study reports a relatively weak and decelerating rise in agricultural diversity over time that was largely decoupled from the strong and continually increasing trend in agricultural dependency on pollinators. Particularly worrisome is a rapid expansion of pollinator‐dependent monocultures in several countries of the Americas and Asia that has resulted in a decrease in agricultural diversity. In these regions, reliance on pollinators is increasing, yet agricultural practices that undermine pollination services are expanding.
Animal pollination can impact food security since many crops depend on pollinators to produce fruits and seeds. However, the effects of projected climate change on crop pollinators and therefore on ...crop production are still unclear, especially for wild pollinators and aggregate community responses. Using species distributional modeling, we assessed the effects of climate change on the geographic distribution of 95 pollinator species of 13 Brazilian crops, and we estimated their relative impacts on crop production. We described these effects at the municipality level, and we assessed the crops that were grown, the gross production volume of these crops, the total crop production value, and the number of inhabitants. Overall, considering all crop species, we found that the projected climate change will reduce the probability of pollinator occurrence by almost 0.13 by 2050. Our models predict that almost 90% of the municipalities analyzed will face species loss. Decreases in the pollinator occurrence probability varied from 0.08 (persimmon) to 0.25 (tomato) and will potentially affect 9% (mandarin) to 100% (sunflower) of the municipalities that produce each crop. Municipalities in central and southern Brazil will potentially face relatively large impacts on crop production due to pollinator loss. In contrast, some municipalities in northern Brazil, particularly in the northwestern Amazon, could potentially benefit from climate change because pollinators of some crops may increase. The decline in the probability of pollinator occurrence is found in a large number of municipalities with the lowest GDP and will also likely affect some places where crop production is high (20% to 90% of the GDP) and where the number of inhabitants is also high (more than 6 million people). Our study highlights key municipalities where crops are economically important and where pollinators will potentially face the worst conditions due to climate change. However, pollinators may be able to find new suitable areas that have the potential to improve crop production. The results shown here could guide policy decisions for adapting to climate change and for preventing the loss of pollinator species and crop production.
Wild and managed pollinators provide a wide range of benefits to society in terms of contributions to food security, farmer and beekeeper livelihoods, social and cultural values, as well as the ...maintenance of wider biodiversity and ecosystem stability. Pollinators face numerous threats, including changes in land-use and management intensity, climate change, pesticides and genetically modified crops, pollinator management and pathogens, and invasive alien species. There are well-documented declines in some wild and managed pollinators in several regions of the world. However, many effective policy and management responses can be implemented to safeguard pollinators and sustain pollination services.
Global trends in nature’s contributions to people Brauman, Kate A.; Garibaldi, Lucas A.; Polasky, Stephen ...
Proceedings of the National Academy of Sciences,
12/2020, Volume:
117, Issue:
51
Journal Article
Peer reviewed
Open access
Declining biodiversity and ecosystem functions put many of nature’s contributions to people at risk. We review and synthesize the scientific literature to assess 50-y global trends across a broad ...range of nature’s contributions. We distinguish among trends in potential and realized contributions of nature, as well as environmental conditions and the impacts of changes in nature on human quality of life. We find declining trends in the potential for nature to contribute in the majority of material, nonmaterial, and regulating contributions assessed. However, while the realized production of regulating contributions has decreased, realized production of agricultural and many material commodities has increased. Environmental declines negatively affect quality of life, but social adaptation and the availability of substitutes partially offset this decline for some of nature’s contributions. Adaptation and substitutes, however, are often imperfect and come at some cost. For many of the contributions of nature, we find differing trends across different countries and regions, income classes, and ethnic and social groups, reinforcing the argument for more consistent and equitable measurement.
The human impact on life on Earth has increased sharply since the 1970s, driven by the demands of a growing population with rising average per capita income. Nature is currently supplying more ...materials than ever before, but this has come at the high cost of unprecedented global declines in the extent and integrity of ecosystems, distinctness of local ecological communities, abundance and number of wild species, and the number of local domesticated varieties. Such changes reduce vital benefits that people receive from nature and threaten the quality of life of future generations. Both the benefits of an expanding economy and the costs of reducing nature's benefits are unequally distributed. The fabric of life on which we all depend-nature and its contributions to people-is unravelling rapidly. Despite the severity of the threats and lack of enough progress in tackling them to date, opportunities exist to change future trajectories through transformative action. Such action must begin immediately, however, and address the root economic, social, and technological causes of nature's deterioration.
Understanding the links between biodiversity-friendly landscapes and human wellbeing is key for supporting policy agendas from local to global scales. United Nations Sustainable Development Goals ...propose full employment (SDG 8) and crop diversity (SDG 2), but it is unclear if there are trade-offs between these goals across rural landscapes worldwide. We tested this idea with agricultural and socio-economic data for 44 countries from all continents during a 15-year period (1999–2013). We show that countries where crop diversity increased also supported more agricultural jobs. Such effects were independent of differences among countries in the size of the agricultural sector or fertilizer use (a proxy for the investment in external inputs and technology incorporation). Greater crop diversity was also compatible with improved crop yields and was not confounded with changes in socio-economic development or economic growth. In general, we found no evidence that the jobs lost in the rural areas were incorporated into other sectors of the economy. Unemployment is a major concern affecting livelihoods all over the world; policies to enhance crop diversity and prevent the loss of associated agricultural jobs are urgently needed.
Policies for Ecological Intensification of Crop Production Garibaldi, Lucas A.; Pérez-Méndez, Néstor; Garratt, Michael P.D. ...
Trends in ecology & evolution (Amsterdam),
April 2019, 2019-Apr, 2019-04-00, 20190401, Volume:
34, Issue:
4
Journal Article
Peer reviewed
Open access
Ecological intensification aims to increase crop productivity by enhancing biodiversity and associated ecosystem services, while minimizing the use of synthetic inputs and cropland expansion. ...Policies to promote ecological intensification have emerged in different countries, but they are still scarce and vary widely across regions. Here, we propose ten policy targets that governments can follow for ecological intensification.
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