Rather like the ENDURE Network itself, landscape ecology is an interdisciplinary science, bringing together scientists with different specialities in a way that holds out intriguing possibilities for improving our understanding of how we can progress in Integrated Pest Management (IPM).
Its focus on landscape at a variety of scales and the interplay between landscapes and the forces at work within them (both natural and human) has already yielded positive results in terms of landscape management for biodiversity conservation purposes.
In contrast, the development of IPM strategies has tended to focus on what happens in the field and its immediate margins. This is a situation ENDURE’s landscape and community ecology research team is seeking to address through examining not just fields but the wider agricultural landscape. By taking a broader view, we should be able to learn more about the relationships between crops, non-crop areas, pests and weeds. Ultimately, we may be able to exploit these relationships to control pests and weeds in a more environmentally friendly way.
The team organised a workshop dedicated to the contributions of landscape ecology to the development of IPM at July’s 2009 European International Association of Landscape Ecology Conference in Salzburg, Austria. The workshop focused on how the distribution of crops and uncultivated areas within a landscape influences pest and weed richness and abundance and their biocontrol by natural enemies.
Worldwide literature review
They took the opportunity to reveal details of their recently completed worldwide literature review of studies investigating the impact of landscape composition on the abundance of arthropod pests and their biological control using natural enemies. This encompassed some 46 studies and 144 independent cases around the world and was based on three hypotheses:
There are, however, some characteristics of pests and cropping systems, as opposed to rare species, for example, that complicate matters. Firstly, unlike rare species, we actively seek to destroy pests (using pesticides, for example) in the crops where they may be most abundant. Thus it could be the case that more crops in the landscape could mean we find fewer pests.
Secondly, some pests do not spend all their life cycle in the crop but re-colonise them each year from another host. This is particularly the case for many aphids, say the researchers, so their abundance also depends on the availability of alternative host plants.
Thirdly, the ENDURE scientists note, their hypotheses are more likely to be true for specialist pests rather than generalist ones.
What was found, and further steps
Globally, they conclude, the picture that emerges is consistent with their expectations concerning conservation biological control: biological control is improved by increasing amounts of non-cultivated habitat in the landscape.
Contrarily, the number of pests in a landscape either decreases or increases with the amount of suitable crop habitat. One possible explanation lies in the way that landscape was described. First there is little information in the publications about the intensity of cropping systems. Second, it is certainly not only the composition of the landscape (cover area of different crops) that matters for pests but also the way they are organised in space. For example, it appears that arable weeds richness within fields is higher in situations where the field is surrounded by many small fields rather than in a situation where it is surrounded by a few large ones. ENDURE scientists thus conclude that studies analysing the effect of landscape structure on pests should be carried out.
Using the knowledge
What can we do with this knowledge and the landscape ecology approach more generally? Firstly, it can provide valuable insights for the various case studies ENDURE is currently conducting. In particular the field vegetable case study, arable system case study and orchard system case study are interested in gleaning information on optimal landscape management for controlling pest abundance.
Further, the team is helping to break new ground by building up and testing hypotheses about the impact of landscapes on weed abundance and diversity, a little studied area where few databases are available and those that are available are in different formats and employ different parameters.
They will be assisted in this work by ENDURE’s team studying weed biology and management (see Weed modellers of the world unite) and the results will feed into both the arable and orchard system case studies.
For more details about the report, contact ENDURE.
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