Forbes contributors publish independent expert analyses and insights.
There are ways to grow food crops without poisoning the soil and landscape with chemical pesticides - by relying on the help of birds and bats!
Intensive agriculture increases food production but it also damages land through habitat loss, deforestation, and soil degradation. As farmers work to meet the needs of a rapidly growing - and hungry - human population, natural ecosystems such as forests and grasslands are converted into agricultural production and farmland, dramatically reducing biodiversity and ecosystem services.
Vineyards - although not essential to feeding hungry humans - are economically and culturally important farmlands that are under threat from the attentions of numerous pests and diseases. Yet only a small number of vineyards are managed using sustainable practices. Further, climate change is enhancing the threat of arthropod pests and diseases, thanks to the increase in unusual weather patterns.
Some vineyards respond to these threats by using more chemical pesticides to keep these pests under control. But outside of breeding pesticide-resistant arthropod pests, these methods don't work well in the long run and, in fact, these chemicals end up accumulating in the landscape and poisoning more than just wildlife and people: they actually accelerate climate change.
Meanwhile, vineyards can support diverse and abundant communities of arthropod-munching predators that deliver effective natural pest control services. Birds and bats, in particular, play a key role by consuming large quantities of insect and arthropod pests. But peculiarly, their contribution to biological pest control - especially in European permanent crops, such as vineyards - remains understudied.
An international study was recently published that makes some progress towards understanding the contributions of birds and bats to natural arthropod control in vineyards. This study was conducted in Hungary, in the western part of the Transdanubian Mountains (Tapolca Basin and Balaton Uplands) and the southern part of the Little Hungarian Plain (Marcal Basin). To conduct this study, the research team selected 12 vineyards (which grow 10 grape varieties; one or two varieties per plantation), six with organic management, and another six with integrated pest management (IPM).
IPM, also known as integrated pest control (IPC), uses both chemical and non-chemical methods for the control of pests. According to the UN's Food and Agriculture Organization, the goal of IPM is to "keep pesticides and other interventions to levels that are economically justified and reduce or minimize risks to human health and the environment. IPM emphasizes the growth of a healthy crop with the least possible disruption to agro-ecosystems and encourages natural pest control mechanisms."
For IPM vineyards, limited chemical inputs are based on monitoring to maintain pest populations below crop injury levels.
In contrast to IPM vineyards, organic vineyards which, according to the Hungarian Central Statistical Office, only comprise 3.2% of all Hungarian vineyards were managed without any applications of herbicides, synthetic insecticides or fertilizers. These organic vineyards typically had smaller areas and yields, and supported a greater diversity of vegetation.
The researchers classified the study vineyards as either 'forested' or 'non-forested' according to their composition and configuration within 500 and 1000 m radius buffers. At both spatial scales, forested landscapes had the highest share of deciduous forests and the greatest connectivity of forest patches, hedgerows, and large groups of trees, whereas non-forested landscapes had a relatively large proportion of arable lands and the greatest vineyard-forest distances. Altogether, the researchers identified three vineyard replications for each factor combination (i.e. organic and forested, organic and non-forested, IPM and forested, IPM and non-forested). The distance between study vineyards was between 1 and 38 km.
The researcher team used exclosures in study vineyards to investigate the effect of birds and bats on arthropod pests affecting ecosystem functions and crop yield considering the local management schemes and contrasting landscape heterogeneity of the vineyards.
The team also collected abundance data of the European grapevine moth, Lobesia botrana, a key grape pest, alongside insects that feed on plants and predatory arthropods in the grapevine canopy, and quantified fruit and leaf damage and other sorts of damages associated with these groups.
As you might expect, vineyards located near forested landscapes had greater bird and bat activity in spring. Although management practices had no measurable effect on the numbers of birds and bats, organic vineyards hosted more canopy-dwelling arthropods and faced greater leaf herbivory - although there was higher predation pressure on caterpillars in organic vineyards.
Did birds and bats reduce fruit damage? Yes: the fruits and leaves on the vines grown in the exclusion treatments consistently showed higher damages, highlighting the ecological and economic value of birds and bats as natural pest control agents.
The numbers and diversity of insectivorous birds and bats were greater in vineyards located close to forested areas.
"The presence of these predators can be promoted by maintaining connected landscapes with native deciduous forest patches, hedgerows, and small groups of trees that offer abundant food sources and suitable nesting or roosting sites," the study's lead author, landscape ecologist Dávid Korányi, said in a statement. Dr Korányi is a postdoctoral researcher at the Centre for Ecological Research at the Hungarian Academy of Sciences.
The study also underscores the importance of local vineyard management in pest control, particularly when the vineyard is organic, since such practices support both beneficial arthropods and natural pest predation in vineyards.
NOTE: questions emailed to the study's lead author, Dávid Korányi, were not unanswered.