Algemeen

Agricultural intensity on the local field or farm scale and on the regional landscape scale affects the organisms utilizing the arable landscape, and may affect ecosystem services and functions. This thesis examines how plants, birds, community composition of ground beetles, and biological control of cereal aphids are affected by local agricultural intensity, organic farming and the surrounding landscape in Sweden and across Europe. The contribution of naturally occurring predator groups to the control of cereal aphid populations in complex and simple arable landscapes is also examined.

The species richness of flower-visiting insects has declined in past decades, raising concerns that the ecosystem service they provide by pollinating crops and wild plants is threatened. The relative commonness of different species with shared ecological traits can play a pervasive role in determining ecosystem functioning, but information on changes in abundances of pollinators over time is lacking. We gathered data on relative abundances of bumble-bee species in Swedish red clover fields during three periods in the last 70 years (1940s, 1960s and present), and on clover seed yields since 1921.

We assessed 30 triticale fields (15 organic vs. 15 conventional) and recorded vascular plants, pollinators, aphids and their predators. Organic fields had five times higher plant species richness and about twenty times higher pollinator species richness compared to conventional fields. Abundance of pollinators was even more than one-hundred times higher on organic fields. In contrast, the abundance of cereal aphids was five times lower in organic fields, while predator abundances were three times higher and predator-prey ratios twenty times higher in organic fields, indicating a significantly higher potential for biological pest control in organic fields.

Pollinators are an essential part of a garden; so essential in fact, that 90 percent of the 250,000 flowering species now in existence rely on them according to the University of Georgia. Bees and butterflies make up the largest group of pollinators; however, the interior design of certain types of flowers makes it impossible for bees or butterflies to pollinate. These plants must rely on other types of insects to seek out the nectar they produce and pollinate them in the process.

New Delhi: Red Pierrot, Common Lime, Plain Tiger, Blue Pansy or the Common Castor may be unfamiliar names to most Indians, although it is likely that most would have seen one or more of the five—the most common butterflies found in India. While it is unlikely that most people would notice their absence, it is almost certain that plants will—butterflies, such as these, help them reproduce. The subcontinent has approximately 1,300 of more than 20,000 butterfly species known, said Kishen Das, a US-based lepidopterist. That’s about 6.5% of the global butterfly diversity. However, the problem is that around 100 of the butterfly species found in India are nearing extinction, according to Surya Prakash, a professor at the department of life sciences at Jawaharlal Nehru University. “Few are aware of the crucial pollination role the butterfly plays, which is second only to the honeybee,” he adds.