Paul van Rijn Maus Sabelis

Transcription

1 Paul van Rijn Maus Sabelis Population Biology Institute for Biodiversity and Ecosystem Dynamics (IBED) University of Amsterdam

2 Landscape ecology > Biodiversity conservation» Dominant view: to reduce the risk of local population extinctions habitats need to expand and be connected to ecological networks (based on Island Biogeography/Metapopulation theory) > Ecologische Hoofdstructuur» Alternative view: to persist year round (some) populations require different habitats nearby (Landscape Complementation).» Why should populations require various habitats? Example & model system: natural pest enemies/control in arable landscapes.

3 Field margin strip Woodlot spring Seasonal habitat shifts autumn Ontogenetic habitat shift Annual Crop Feeding Ovipositing Field scale Foraging Landscape scale Dispersal» Model approach: What is the optimal landscape composition for natural pest control?

4 » Hoverflies moving in field with crop and flower strip searching for floral resources (feeding) when energy level is low aphid patches (ovipositing) when energy level is high 1 Model: Distribution of hoverflies and aphids 1 Field: Hoverfly eggs+larvae (normalized, 6potato fields ) 0,75 0,5 0,25 adults eggs larval biomass aphids 0,5 0 0, Distance to flower strip (m) 1, Distance to flower strip (m) Impact of predatory hoverflies is restricted to meter from flower source

5 Focal population Ad. Juv. Ad. Juv. Ad. Resource Pollen/ Nectar Aphids Aphids Pollen/ Nectar Months: Habitat Scrubs and trees Arable crop Flowering field margin 1. Stage structured (set of (delay) differential equations) 2. Habitat structured (set of DE s for each habitat) 3. Dispersal between habitats assumes optimal foraging 4. Resources seasonally driven

6 Aphid growth Floral resources 1 Apr. May June July Aug. Sep. Oct. Woodlot H1: woodlot H1f: woodlot flowers Crop field H2: winter wheat H2f: flower strip Crop field H3: potato H3f: flower strip Contribution of various landscape elements to natural pest suppression Effect of habitat management on natural pest suppression no predators mean aphid density wheat field potato field mean aphid density 200 wheat field potato field no flower potato 150 no flower wheat no wheat field 100 no woody habitat 50 complete landscape 0 0,2 0,4 0,6 0, Flowering date wheat

7 » Hoeksche Waard Association of municipalities (SOHW) Agro environmental organisation (ANV de Rietgors ) Organised Farmers (LTO noord) Advisory service HW op de Kaart (HWodKa) Nature conservation Hoeksewaards Landschap (HWL)» Waterschap Hollandse Delta (WSHD) M. Vonk J. Zevenbergen J. de Geus A. Klompe» Province Zuid Holland M. Wiersema» Ministery Infrastructure & Environment (I&M) G. Eshuis» Project Akkerranden Flevoland A. Visser

8 Hoeksche Waard: Yearly: monitoring based advise on management of field margin strips, ditches and road verges for support group Agroranden (chaired by ANV Rietgors) and SOHW. 2012, July: workshop (3 OBW projects together) at SOHW, including Landscape design game 2013, April: workshop (3 OBW projects) at PPO Westmaas: inventory (matrix) of landscape functions, interests, possible conflicts and synergies Request to provide focus areas for which research based landscape improvements are designed and implemented 2014: Series of meetings on the pilot Duurzame landbouw in een duurzaam landschap ; Working group green blue veining 2015: workshop (planned) on possible measures to implement results.

9 1. Woody habitats are important for the support of natural pest enemies especially during spring. 2. Flower strips can enhance biological pest control, but their impact is spatially limited (max m). 3. To be affective field margin strips should start flowering synchronous with aphid development in the adjacent crop. 4. Early aphid supporting crops (such as wheat), when bordered by flower strips, can provide natural pest enemies for later crops (such as potato). 5. Various habitat types are complementary in their support of natural enemy populations and related ecosystem services. An optimal ( complete ) landscape is also defined by the right proportions of habitats.

10 1. We may need to look for measures to support woody habitats locally. The present policy in our area is to keep it open (SOHW, ANV, HWL). 2. Clearly, an even finer network of flowers strips is needed, preferably with strips on both sides of arable fields (ANV, Farmers). 3. We are already promoting the early sowing of field margin strips, but sometimes the weather does not cooperate (ANV). 4. When making our crop rotation plans we should take the potential support of natural pest enemies into account as well (ANV, Farmers). 5. The study clearly indicates that our agro environmental policy should also take ecosystem services, such as natural pest control, into account. Current financial instruments (CAP) and busyness models are insufficient to support the measures needed (ANV, Farmers, SOHW).