Loss Of Wild Insects Hurts Crop Yield
By Countercurrents.org
01 March, 2013
Countercurrents.org
Practicing agriculture without considering environment is unimaginable. Findings from two studies mentioned below provide important insights.
Researchers studying data from 600 fields in 20 countries have found that managed honey bees are not as successful at pollinating crops as wild insects, primarily wild bees, suggesting the continuing loss of wild insects in many agricultural landscapes has negative consequences for crop harvests [1].
The study, which prompts an urgent call to maintain and manage pollinator diversity for long-term agricultural production, is published in the journal Science.
The 50 international researchers, including Lawrence Harder, professor in the Department of Biological Sciences in the Faculty of Science at the University of Calgary, analyzed data from 41 crop systems around the world including fruits, seeds, nuts, and coffee to examine the consequences of having abundant wild pollinators for crop pollination.
"Our study demonstrates that production of many fruit and seed crops that make diets interesting, such as tomatoes, coffee and watermelon, is limited because their flowers are not adequately pollinated," says Harder. "We also show that adding more honey bees often does not fix this problem, but that increased service by wild insects would help."
Flowers of most crops need to receive pollen before making seeds and fruits, a process that is enhanced by insects that visit flowers. These pollinators, including bees, flies, butterflies and beetles, usually live in natural or semi-natural habitats, such as the edges of forests, hedgerows or grasslands. As these habitats are lost, primarily owing to conversion to agriculture, the abundance and diversity of pollinators decline and crops receive fewer visits from wild insects.
The study found that the proportion of flowers producing fruits was considerably lower in sites with fewer wild insects visiting crop flowers. Therefore, the reduction of wild insects in agricultural landscapes will likely impact both our natural heritage and agricultural harvest.
"Paradoxically, most common approaches to increase agricultural efficiency, such as cultivation of all available land and the use of pesticides, reduce the abundance and variety of wild insects that could increase production of these crops," says Harder. "Our study highlights the benefits of considering this paradox in designing and implementing agricultural systems."
The study suggests that new practices for integrated management of both honey bees and wild insects will enhance global yields of animal-pollinated crops and promote long-term agricultural production. These practices should include conservation or restoration of natural or semi-natural areas within croplands, promotion of a variety of land use, addition of diverse floral and nesting resources, and more prudent use of insecticides that can kill pollinators.
IMPROVING CLIMATE PROTECTION IN AGRICULTURE SECTOR
Agriculture is responsible for around ten to twelve percent of all GHG attributable to human activities. This raises the question of how these emissions could be reduced [2].
A recent study has investigated -- for the first time -- the full range of factors that contribute to GHG emissions, namely soil and climate conditions, the agricultural model and the farming intensity on both organic and conventional holdings. The study has enabled scientists to develop a new model that will allow agricultural landholders to determine and improve their climate balance.
As part of the study, scientists investigated 40 organic and 40 conventional agricultural holdings across Germany's four agricultural regions. They focused exclusively on crop and dairy farms. The scientists recorded all relevant climate gas streams during the entire production process, including methane, nitrous oxide and carbon dioxide. In the case of dairy farms, they also factored in the purchase of soybean meal from South America and all related GHG emissions.
Strategies for improving climate balance
Fossil fuels, above all diesel, are one of the main sources of CO2 emissions in agriculture. However, GHG are also emitted during the manufacture of mineral nitrogen fertilizers and pesticides, agricultural machines and equipment.
"There are different ways of improving a farm's climate balance," explains Professor Kurt-Jürgen Hülsbergen from Technische Universität München (TUM). "One effective strategy is for landholders to grow feed themselves rather than purchase soy from another source. Farms can also streamline production processes and deploy modern technology to obtain higher yields without increasing the amount of energy required."
In crop farming, increasing nitrogen efficiency is a key factor. High levels of nitrous oxide are released into the environment if crops are unable to utilize all of the nitrogen fertilizer that was spread. The production of nitrogen fertilizer is also energy intensive, which further increases the climate balance of unused nitrogen.
The GHG CO2 can be stored long term as humus in the soil, and thus eliminated from the climate balance. "This can be achieved by planting legumes as part of a diversified crop rotation strategy," explains Professor Gerold Rahmann at the Thünen Institute. "Using soil less intensively and applying organic fertilizer also helps."
Topping the charts: organic versus conventional farming
Organic farming is more energy efficient and produces less land-specific CO2 emissions. This advantage, however, is offset by the significantly lower yields achieved through organic farming practices. The pilot organic crop farms produce around twenty percent less emissions per yield unit than conventional holdings.
Organic dairy farms use more plant fodder grown on site and do not import soybean meal. This strategy pays off, according to Hülsbergen: "The pilot organic farms we looked at emit around 200 grams less CO2 per kilogram of milk than conventional farms with the same milk yield."
Most interestingly, the investigations show that yields and GHG emissions fluctuate significantly between different organic farms in some cases to an even greater extent than the fluctuations between organic and conventional holdings. This demonstrates that the individual know-how of farm managers plays an important role in the greenhouse gas balance and that there is significant potential for improvement at individual farms.
Putting theory into practice
This is the first time that a study has provided a 360-degree overview of climate-relevant factors impacting all emissions related to livestock and crop farming. "We have a workable model that will enable us to identify the causes of low energy efficiency and high greenhouse gas emissions," adds Hülsbergen. "We are now optimizing this model so that it can be used directly by climate change advisors in the agricultural sector."
The study was carried out from 2009 to 2012 as part of a collaborative project between TUM, the Thünen Institute, the University of Bonn, the Martin-Luther-Universität Halle Wittenberg and Bioland Beratung.
Note:
[1] Story Source:
The story is reprinted from materials provided by University of Calgary, via EurekAlert!, a service of AAAS.
Journal Reference:
Lucas A. Garibaldi, Ingolf Steffan-Dewenter, Rachael Winfree, Marcelo A. Aizen, Riccardo Bommarco, Saul A. Cunningham, Claire Kremen, Luísa G. Carvalheiro, Lawrence D. Harder, Ohad Afik, Ignasi Bartomeus, Faye Benjamin, Virginie Boreux, Daniel Cariveau, Natacha P. Chacoff, Jan H. Dudenhöffer, Breno M. Freitas, Jaboury Ghazoul, Sarah Greenleaf, Juliana Hipólito, Andrea Holzschuh, Brad Howlett, Rufus Isaacs, Steven K. Javorek, Christina M. Kennedy, Kristin Krewenka, Smitha Krishnan, Yael Mandelik, Margaret M. Mayfield, Iris Motzke, Theodore Munyuli, Brian A. Nault, Mark Otieno, Jessica Petersen, Gideon Pisanty, Simon G. Potts, Romina Rader, Taylor H. Ricketts, Maj Rundlöf, Colleen L. Seymour, Christof Schüepp, Hajnalka Szentgyörgyi, Hisatomo Taki, Teja Tscharntke, Carlos H. Vergara, Blandina F. Viana, Thomas C. Wanger, Catrin Westphal, Neal Williams, and Alexandra M. Klein. Wild Pollinators Enhance Fruit Set of Crops Regardless of Honey Bee Abundance. Science, 2013; DOI: 10.1126/science.1230200
Source:
University of Calgary (2013, February 28). Loss of wild insects hurts crops around the world. ScienceDaily. Retrieved March 1, 2013, from
http://www.sciencedaily.com /releases/2013/02/130228155622.htm
[2] Story Source:
The story is reprinted from materials provided by Technische Universitaet Muenchen.
Source:
Technische Universitaet Muenchen (2013, February 28). Improving climate protection in the agricultural sector. ScienceDaily. Retrieved March 1, 2013, from
http://www.sciencedaily.com /releases/2013/02/130228124146.htm
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