TY  - JOUR
A1  - Krauss, Jochen
A1  - Gallenberger, Iris
A1  - Steffan-Dewenter, Ingolf
T1  - Decreased Functional Diversity and Biological Pest Control in Conventional Compared to Organic Crop Fields
N2  - Organic farming is one of the most successful agri-environmental schemes, as humans benefit from high quality food, farmers from higher prices for their products and it often successfully protects biodiversity. However there is little knowledge if organic farming also increases ecosystem services like pest control. We assessed 30 triticale fields (15 organic vs. 15 conventional) and recorded vascular plants, pollinators, aphids and their predators. Further, five conventional fields which were treated with insecticides were compared with 10 non-treated conventional fields. 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. Insecticide treatment in conventional fields had only a short-term effect on aphid densities while later in the season aphid abundances were even higher and predator abundances lower in treated compared to untreated conventional fields. Our data indicate that insecticide treatment kept aphid predators at low abundances throughout the season, thereby significantly reducing top-down control of aphid populations. Plant and pollinator species richness as well as predator abundances and predator-prey ratios were higher at field edges compared to field centres, highlighting the importance of field edges for ecosystem services. In conclusion organic farming increases biodiversity, including important functional groups like plants, pollinators and predators which enhance natural pest control. Preventative insecticide application in conventional fields has only short-term effects on aphid densities but long-term negative effects on biological pest control. Therefore conventional farmers should restrict insecticide applications to situations where thresholds for pest densities are reached.
KW  - Landwirtschaft
Y1  - 2011
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-69005
ER  - 
TY  - JOUR
A1  - McCarthy, Michael A.
A1  - Moore, Alana L.
A1  - Krauss, Jochen
A1  - Morgan, John W.
A1  - Clements, Christopher F.
T1  - Linking Indices for Biodiversity Monitoring to Extinction Risk Theory
T1  - Conectando Índices para el Monitoreo de la Biodiversidad con la Teoría de Riesgo de Extinción
JF  - Conservation Biology
N2  - Biodiversity indices often combine data from different species when used in monitoring programs. Heuristic properties can suggest preferred indices, but we lack objective ways to discriminate between indices with similar heuristics. Biodiversity indices can be evaluated by determining how well they reflect management objectives that a monitoring program aims to support. For example, the Convention on Biological Diversity requires reporting about extinction rates, so simple indices that reflect extinction risk would be valuable. We developed 3 biodiversity indices that are based on simple models of population viability that relate extinction risk to abundance. We based the first index on the geometric mean abundance of species and the second on a more general power mean. In a third index, we integrated the geometric mean abundance and trend. These indices require the same data as previous indices, but they also relate directly to extinction risk. Field data for butterflies and woodland plants and experimental studies of protozoan communities show that the indices correlate with local extinction rates. Applying the index based on the geometric mean to global data on changes in avian abundance suggested that the average extinction probability of birds has increased approximately 1% from 1970 to 2009.
N2  - Los índices de biodiversidad combinan frecuentemente los datos de diferentes especies cuando se usan en los programas de monitoreo. Las propiedades heurísticas pueden sugerir índices preferidos, pero carecemos de medios objetivos para discriminar a los índices con propiedades heurísticas similares. Los índices de biodiversidad pueden evaluarse al determinar qué tan bien reflejan los objetivos de manejo que un programa de monitoreo busca apoyar. Por ejemplo, la Convención sobre la Diversidad Biológica requiere reportar las tasas de extinción, así que los índices que reflejan el riesgo de extinción serían valiosos. Desarrollamos 3 índices de biodiversidad que se basan en modelos sencillos de viabilidad de población y que relacionan el riesgo de extinción con la abundancia. Basamos el primer índice en la media geométrica de la abundancia de especies, y el segundo en una media de poder m´as general. En el tercer índice integramos la media geométrica y la tendencia. Estos índices requieren los mismos datos que índices previos, pero también se relacionan directamente con el riesgo de extinci´on. La información de campo sobre mariposas y plantas de bosque, y los estudios experimentales de comunidades protozoarias, muestran que los índices se correlacionan con las tasas locales de extinción. Al aplicar el índice basado en la media geométrica sobre los datos globales de los cambios en la abundancia de aves, sugirió que la probabilidad de extinción promedio de aves ha incrementado aproximadamente 1% desde 1970 hasta 2009.
KW  - biodiversity index
KW  - biodiversity measure
KW  - extinction risk
KW  - geometric mean
KW  - riesgo de extinción
KW  - medida de la biodiversidad
KW  - media geométrica
KW  - índice de biodiversidad
Y1  - 2014
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-121218
VL  - 28
IS  - 6
ER  - 
TY  - JOUR
A1  - Kleijn, David
A1  - Winfree, Rachael
A1  - Bartomeus, Ignasi
A1  - Carvalheiro, Luísa G.
A1  - Henry, Mickael
A1  - Isaacs, Rufus
A1  - Klein, Alexandra-Maria
A1  - Kremen, Claire
A1  - M'Gonigle, Leithen K.
A1  - Rader, Romina
A1  - Ricketts, Taylor H.
A1  - Williams, Neal M.
A1  - Adamson, Nancy Lee
A1  - Ascher, John S.
A1  - Báldi, András
A1  - Batáry, Péter
A1  - Benjamin, Faye
A1  - Biesmeijer, Jacobus C.
A1  - Blitzer, Eleanor J.
A1  - Bommarco, Riccardo
A1  - Brand, Mariette R.
A1  - Bretagnolle, Vincent
A1  - Button, Lindsey
A1  - Cariveau, Daniel P.
A1  - Chifflet, Rémy
A1  - Colville, Jonathan F.
A1  - Danforth, Bryan N.
A1  - Elle, Elizabeth
A1  - Garratt, Michael P. D.
A1  - Herzog, Felix
A1  - Holzschuh, Andrea
A1  - Howlett, Brad G.
A1  - Jauker, Frank
A1  - Jha, Shalene
A1  - Knop, Eva
A1  - Krewenka, Kristin M.
A1  - Le Féon, Violette
A1  - Mandelik, Yael
A1  - May, Emily A.
A1  - Park, Mia G.
A1  - Pisanty, Gideon
A1  - Reemer, Menno
A1  - Riedinger, Verena
A1  - Rollin, Orianne
A1  - Rundlöf, Maj
A1  - Sardiñas, Hillary S.
A1  - Scheper, Jeroen
A1  - Sciligo, Amber R.
A1  - Smith, Henrik G.
A1  - Steffan-Dewenter, Ingolf
A1  - Thorp, Robbin
A1  - Tscharntke, Teja
A1  - Verhulst, Jort
A1  - Viana, Blandina F.
A1  - Vaissière, Bernard E.
A1  - Veldtman, Ruan
A1  - Ward, Kimiora L.
A1  - Westphal, Catrin
A1  - Potts, Simon G.
T1  - Delivery of crop pollination services is an insufficient argument for wild pollinator conservation
JF  - Nature Communications
N2  - There is compelling evidence that more diverse ecosystems deliver greater benefits to people, and these ecosystem services have become a key argument for biodiversity conservation. However, it is unclear how much biodiversity is needed to deliver ecosystem services in a cost- effective way. Here we show that, while the contribution of wild bees to crop production is significant, service delivery is restricted to a limited subset of all known bee species. Across crops, years and biogeographical regions, crop-visiting wild bee communities are dominated by a small number of common species, and threatened species are rarely observed on crops. Dominant crop pollinators persist under agricultural expansion and many are easily enhanced by simple conservation measures, suggesting that cost- effective management strategies to promote crop pollination should target a different set of species than management strategies to promote threatened bees. Conserving the biological diversity of bees therefore requires more than just ecosystem-service-based arguments.
KW  - ecosystem services
KW  - european countries
KW  - abundance
KW  - native bees
KW  - biodiversity conservation
KW  - plant diversity
KW  - fruit set
KW  - productivity
KW  - decline
KW  - pollen
Y1  - 2015
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-151879
VL  - 6
IS  - 7414
ER  - 
TY  - JOUR
A1  - Dainese, Matteo
A1  - Schneider, Gudrun
A1  - Krauss, Jochen
A1  - Steffan-Dewenter, Ingolf
T1  - Complementarity among natural enemies enhances pest suppression
JF  - Scientific Reports
N2  - Natural enemies have been shown to be effective agents for controlling insect pests in crops. However, it remains unclear how different natural enemy guilds contribute to the regulation of pests and how this might be modulated by landscape context. In a field exclusion experiment in oilseed rape (OSR), we found that parasitoids and ground-dwelling predators acted in a complementary way to suppress pollen beetles, suggesting that pest control by multiple enemies attacking a pest during different periods of its occurrence in the field improves biological control efficacy. The density of pollen beetle significantly decreased with an increased proportion of non-crop habitats in the landscape. Parasitism had a strong effect on pollen beetle numbers in landscapes with a low or intermediate proportion of non-crop habitats, but not in complex landscapes. Our results underline the importance of different natural enemy guilds to pest regulation in crops, and demonstrate how biological control can be strengthened by complementarity among natural enemies. The optimization of natural pest control by adoption of specific management practices at local and landscape scales, such as establishing non-crop areas, low-impact tillage, and temporal crop rotation, could significantly reduce dependence on pesticides and foster yield stability through ecological intensification in agriculture.
KW  - ecosystem services
KW  - agroecology
Y1  - 2017
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-158621
VL  - 7
ER  -