Friday, November 20, 2015
The pesticide treadmill explained
A new study confirms what organic farmers have known all the time: that pest damage is reduced by more diverse production and that the use of pesticides creates pest problems.
In recent decades, there has been a steady increase in the amount of pesticides marketed for argicultural use. In the European Union alone, more than 200,000 tonnes of pesticides (active ingredients) are used annually. Between 2005 and 2010, the total volume of global sales rose from US$ 31 billion to US$ 38 billion. The amount of pesticides used internationally has risen fifty-fold since 1950. China is now the country that both uses and produces the largest amounts of pesticides (PAN Germany, Pesticides and health hazards, Facts and figures).
Pests are major challenges to food security, and responses to pests can incur unintended socio-economic and environmental costs and massive damage to health. The UNEP Cost of Inaction Report (2012) reveals that the costs of injury (lost work days, outpatient medical treatment, and inpatient hospitalization) from pesticide poisonings, in Sub-saharan Africa alone, amounted to USD $4.4 billion in 2005. Another study suggests that the major economic and environmental losses due to the use of pesticides in the United States amounted to USD $1.5 billion in pesticides resistance and USD $1.4 billion in crop losses, and USD $2.2 billion in bird losses. (Global Chemicals Outlook: Towards Sound Management of Chemicals)
Proponents of organic farming and agro-ecology "know" that increasing diversity in the production system will generally decrease pest problems. This is not to say that there can't be serious pest problems also in organic farms or in other farms which have high diversity. It can, but by and large damage will be less according to my observations in some fifty countries of the world with very diverse production system.
There is, however, a poor understanding of how biodiversity contributes to ecosystem functions and influences pest populations on farms.To address this gap, a new study examines how species diversity and the network of linkages in species’ abundances affect pest abundance on maize farms across the Northern Great Plains in the U.S. Maize (corn) currently occupies nearly 5% of the land surface of the contiguous United States and 95% of certain counties. Despite the tremendous efforts to combat pests - $3.2 billion was spent to manage maize pests in the United States during 2013 - comprehensive bioinventories of the arthropod species that occur within this habitat are scarce.
The study show that "increased species diversity, community evenness, and linkage strength and network centrality within a biological network all correlate with significantly reduced pest populations. This supports the assertion that reduced biological complexity on farms is associated with increased pest populations and provides a further justification for diversification of agroecosystems to improve the profitability, safety, and sustainability of food production systems.increased species diversity, community evenness, and linkage strength and network centrality within a biological network all correlate with significantly reduced pest populations."
For example, reducing tillage, using cover crops, intercropping, crop rotations, etc. should help increase biodiversity. In line with this, the research results show that using pest management practices that reduce biodiversity and species interactions will create systems where pests will continually pose problems (i.e., the pesticide treadmill). This finding provides further justification for diversification of agroecosystems to improve the profitability, safety, and sustainability of food production systems.
The full paper is available at http://advances.sciencemag.org/content/1/6/e1500558
Trading biodiversity for pest problems
By Jonathan G. Lundgren, Scott W. Fausti
Science Advances31 Jul 2015 : e1500558