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Plant, Land and Pest Diversity Relationship

by Edward Buckler
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Plant, Land, and Pest Diversity Relationship

As agriculture develops, it becomes more intense and less complex. Aiming large cropping fields, more arable land, and less plant diversity with less rotational crops.

Ecological theories usually state that diversity contributes to the stability of biological ecosystems. Assistant Professor in Environmental Sciences, Ashley Larsen, at the University of California, wondered how these principles apply to agriculture landscapes, especially those associated with pests.

Larsen and Frederick Noack, her colleague, evaluated 13-year data from Kern County, California, which constantly tops the list of the country’s most productive agricultural districts, and found that less diverse lands with respect to pesticide use led to more variability in crop productivity.

The principle of greater diversity would stabilize an ecosystem originated around the 1940s, at a fairly initial stage in the development of the ecological area. Over the years, this theory has met with some uncertainties, and recently, interest in studying this relationship has increased again.

Kern County proved to be an excellent opportunity to study the pant, land, and pest diversity relationship for Larsen and Frederick Noack. This case helped them understand, how variations in plants and landscape diversities affect plant pest populations.


Effects of biodiversity in agriculture

“There has been a shift towards larger farms in the US, instead of small family businesses, we now have much larger agricultural firms,” Larsen said.

This was complemented by a trend towards increasing field sizes and decreasing plant diversity. She alleged that this all be attributed to farmers who have taken advantage of their economic strengths.

Although Kern County maintains huge agriculture records still no one was tracking pest populations as such.


Therefore, the researchers had to practice an indirect argument: the use of insecticides to explain the ecology of crop pests. Late, this proved to be very effective and increased the impact of their results.


When you introduce the usage of insecticides as a factor into research, it turns to an impact on the environment and food security, instead of just an ecological theory about diversity and stability.


Researches searched the records of Kern from 2005 to 2017, focusing on factors, field size, number, and variety of lands planted. During their search, they found an increase in cropland in rural areas and pesticide levels in large fields, whereas diversity impacted oppositely.


The larger the field size, the faster the area becomes larger than the perimeter. And means more overflow from neighboring predators, such as birds, ladybugs, and spiders which feed on agricultural pests.

A peripheral habitat around smaller fields provides a place for competitors and predators to keep the populations of pests under control. As the field center is closer to the edge in small fields, therefore benefits of pest reduction increase in small fields. Landscapes with different crops and vegetation are also correlated with pesticide use and variability.

Larsen and Noack’s recommends minimizing the use of insecticides and increase food production with several organic strategies. So, the pest population diversity can be maintained and the impact of pesticides on the environment, and humans can be reduced.

Landscape scaling is also very important to maintain an ideal plant, land, and pest diversity relationship.

Source: Larsen and Naock, 2020

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