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Dear Friends and Colleagues

Intensified Agriculture Leads to Yield Reductions but Biodiversity Is Beneficial for Crop Production

Over the past half-century, the need to feed a growing world population has led to markedly expanded and intensified agricultural production. This transformation has led to the degradation of the global environment. The loss of biodiversity can disrupt key ecosystem services to agriculture, such as crop pollination and biological pest control, which underpin the final provisioning service of crop production. Around 20% of the world’s agricultural areas yield less than they did 20 years ago (Item 1).

A study (Item 2) compiled an extensive database comprising 89 studies that measured richness and abundance of pollinators, pest natural enemies, and associated ecosystem services at 1,475 sampling locations around the world. The researchers partitioned the relative importance of richness, total abundance, and evenness in driving biodiversity–ecosystem services relationships. They found clear evidence that the richness of service-providing organisms positively influenced ecosystem service delivery. This was detected for both pollination and pest control in almost all the studies.

Furthermore, landscape simplification indirectly affected ecosystem services by reducing both the richness and abundance of service-providing organisms. Roughly a third of the negative effects of landscape simplification on pollination were due to a loss in pollinator richness. This effect was even greater for pest control where natural enemy richness mediated about 50% of the total effect of landscape simplification. In turn, there was decreased crop production. Insecticide use undermined the full potential of natural pest control.

In sum, the study found strong evidence for positive biodiversity–ecosystem service relationships, highlighting that managing landscapes to enhance the richness of service-providing organisms is a promising pathway toward a more sustainable food production globally. Preserving biodiversity-driven services will consistently confer greater resilience to agroecosystems, such that we could expect improved crop production under a broader range of potential future conditions.

With best wishes,

Third World Network
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Item 1

LOSS OF BIODIVERSITY CAUSES YIELD REDUCTIONS

Rural 21
25 Oct 2019
https://www.rural21.com/english/news/detail/article/loss-of-biodiversity-causes-yield-reductions-00003446/

 Around 20 per cent of the world’s agricultural areas yields less than it did 20 years ago. The disruption of biological pest control and pollination occurring in monotonous agricultural landscapes leads to significant yield reductions, researchers say.

Can ecosystem services like biological pest control and pollination be maintained by a few dominant species or do they rely on high richness?  The greater the diversity of species and the smaller-scaled the agricultural landscape, the greater are the positive effects of natural service providers, said researchers from the Julius-Maximilians-Universität (JMU) Würzburg, Germany, in October 2019. With more than 100 participating scientists, they evaluated 89 studies investigating the connection between land use, biodiversity and the free services of ecosystems.

The studies took place at almost 1500 sites worldwide – from corn fields in the USA to oilseed rape fields in southern Sweden, coffee plantations in India, mango plantations in South Africa to cereal crops in the Alps.

In many respects, nature is an outstanding service provider for agriculture. Bees and bumble bees pollinate fruit trees and other crops. Parasitoid wasps and predatory beetles eat pests that would otherwise attack crops. In addition, there are many other animal species that work free of charge for humans.

However, where huge, monotonously planted areas predominate, the diversity and abundance of useful organisms are significantly reduced, having a negative impact on yields. In order to sustainably secure nature’s free services, humans must ensure the greatest possible biodiversity, the researchers say. It is not enough to rely on just a few species as pollinators or pest regulators.

It has been controversially discussed whether a few, dominant species are sufficient to maintain crop pollination and pest control services. This study provides strong evidence that a high number of different species is crucially important to ensure services by arthropods and maintain high yields, the researchers state.

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Item 2

A GLOBAL SYNTHESIS REVEALS BIODIVERSITY-MEDIATED BENEFITS FOR CROP PRODUCTION

Matteo Dainese et al.
Science Advances 
Vol. 5, no. 10, eaax0121
16 Oct 2019
DOI: 10.1126/sciadv.aax0121
https://advances.sciencemag.org/content/5/10/eaax0121

 Abstract

Human land use threatens global biodiversity and compromises multiple ecosystem functions critical to food production. Whether crop yield–related ecosystem services can be maintained by a few dominant species or rely on high richness remains unclear. Using a global database from 89 studies (with 1475 locations), we partition the relative importance of species richness, abundance, and dominance for pollination; biological pest control; and final yields in the context of ongoing land-use change. Pollinator and enemy richness directly supported ecosystem services in addition to and independent of abundance and dominance. Up to 50% of the negative effects of landscape simplification on ecosystem services was due to richness losses of service-providing organisms, with negative consequences for crop yields. Maintaining the biodiversity of ecosystem service providers is therefore vital to sustain the flow of key agroecosystem benefits to society.

 


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