POLLINATORS POLLINATION AND FOOD PRODUCTION

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THE ASSESSMENT REPORT ON POLLINATORS, POLLINATION AND FOOD PRODUCTION 100 2. DRIVERS OF CHANGE OF POLLINATORS, POLLINATION NETWORKS AND POLLINATION shift in the areas suitable for passion fruit pollinators by 2050. Polce et al. (2014) modelled the present and future distributions of orchard crops in the UK, and 30 species of bees and hoverflies known to visit fruit tree flowers under a medium emissions scenario. They showed that the present distribution of orchards in the UK largely overlaps with areas of high pollinator richness, but there could be a substantial geographical mismatch in the future (2050), as the area with climate most suitable for orchards moves substantially north and west. Future ranges also have been projected for some bee species using the approach in Europe (Roberts et al. 2011) and South Africa (Kuhlmann et al. 2012), and in particular for bumble bees and butterflies on a European continental scale (see Box 2.6.1). Giannini et al. (2012) modelled a decrease in bee habitats due to climate change in Brazil. However, the possibility that pollinators gradually change their target plant species is not taken into account in such approaches. There are indications for such shifts (Schweiger et al., 2008) which would mean that there is no necessity to move with the current plant species. Instead, this is a component of novel ecosystems evolving under climate change. Due to considerable differences in larval resources among the different pollinator groups, it is uncertain whether the impacts of climate change on bees and syrphid flies will show similar patterns as those for butterflies and bumble bees (Settele et al., 2008, Rasmont et al., 2015a). Carvalheiro et al. (2013) show that bumble bees and butterflies are far more prone to local and regional extinction than other bees or hoverflies, and Kerr et al. (2015) show the drastic effects of climate change on bumble bees. However, in all groups, landscape connectivity, the mobility of species and effects on plants and on floral resources are important and widely unknown factors, which might drastically change the expected future impacts. to regulate the temperature inside the colony (hive) by thermogenesis or cooling, this species seems not directly threatened by global warming. While for the majority of species climate space itself is already limiting (e.g., on the pollinators’ physiology), all pollinators that more or less depend on certain plants, potentially suffer indirectly because of climate change impacts on these plants (Schweiger et al., 2008; Schweiger et al., 2010; Schweiger et al., 2012). In butterflies the nectar plants are more independent from the insect in their development (as there is mostly no specific link for the plants’ pollination), while one might expect impacts in “tighter” pollination systems. The absence of a pollinator could mean absence of a pollination-dependent plant and vice versa (Biesmeijer et al. 2006). These effects can be expected only for the rare cases of high specialization, and indeed Carvalheiro et al. (2013) reanalyzed the data from Biesmeijer et al., (2006) and found that declines are not parallel in time. Hoover et al. (2012) have shown, in a pumpkin model system, that climate warming, CO 2 enrichment and nitrogen deposition non-additively affect nectar chemistry (among other traits), thereby altering the plant’s attractiveness to bumble bees and reducing the longevity of the bumble bee workers. This could not be predicted from isolated studies on individual drivers. Generally, it can be assumed that climate change results in novel communities, i.e. creation of species assemblages that have not previously co-existed (Schweiger et al., 2010). As these will have experienced a much shorter (or even no) period of coevolution, substantial changes in pollination networks are to be expected (Tylianakis et al., 2008; Schweiger et al., 2012). This might generally result in severe changes in the provision of services (like pollination), especially in more natural or wild conditions (Montoya and Raffaelli, 2010). 2.6.2.4 Further climate change impacts on pollinators Climate change might modify the balance between honey bees and their environment (including diseases). Le Conte and Navajas (2008) state that the generally observed decline of honey bees is a clear indication for an increasing susceptibility against global change phenomena, with pesticide application, new diseases and other stress (and a combination of these) as the most relevant causes. Honey bees also have shown a large capacity to adjust to a large variety of environments (not at least as they are often managed and hence may be buffered accordingly) and their genetic variability should allow them to also cope with climatic change, which is why the preservation of genetic variability within honey bees is regarded as a central aim to mitigate climate change impacts (Le Conte and Navajas, 2008). Also, due to the great capacity of the honey bee Climate change-induced changes in habitat encompass i) shifts in habitat distributions that cannot be followed by species, ii) shifts in distribution of species that drive them outside their preferred habitats and iii) changes in habitat quality (Urban et al., 2012). However, these phenomena are not yet widespread, while models of future shifts in biome and vegetation type (and species distributions, see previous sections) suggest that within the next few decades many species could have been driven out of their preferred habitats due to climate change (Urban et al., 2012). Wiens et al. (2011) also find that climate change may open up new opportunities for protecting species in areas where climate is currently unsuitable. Indeed, in some cases climate change may allow some species to move into areas of lower current or future land use pressure (Bomhard et al., 2005). These and other studies strongly argue for a rethinking of protected areas networks and of the importance of the habitat matrix outside protected areas to enhance the ecosystem
THE ASSESSMENT REPORT ON POLLINATORS, POLLINATION AND FOOD PRODUCTION FIGURE 2.6.2 Butterfly and bumblebee examples of climate spaces within the GRAS scenario, according to different distributional characteristics (maps: bumblebees after Rasmont et al., 2015a, butterflies after Settele et al., 2008). HHHR (extremely high climate change risk); HHR (very high climate change risk); HR (high climate change risk); AUC (Area under curve – the closer the value is to 1, the better is the model). Characteristics Bumblebee examples Butterfly examples • Boreo-alpine species • Extremely high climate change risk independent of dispersal as the climatic space vanishes Bombus polaris Category: HHHR Net change (% area) 50 Gain Photo: P. Rasmont Colias hecla Category: HHHR Net change (% area) 50 Gain Photo: B. Söderström 0 0 -50 -50 Loss -100 -99 -99 No Full Dispersal Loss -100 -98 -98 No Full Dispersal • Patchy distribution pattern • Complete loss with “no dispersal” Bombus incertus Category: HHHR Photo: P. Rasmont Polyommatus dolus Category: HHHR Photo: A. Vliegenthart 101 • Much lower losses under “full dispersal” • More widespread species • High losses under “no dispersal” • Moderate losses with “full dispersal” Bombus pomorum Category: HHHR Net change (% area) 50 Gain Loss 0 -50 -100 -100 -79 No Full Dispersal Net change (% area) 50 Gain 0 Photo: D. Genoud Apatura iris Category: HHR Net change (% area) 50 Gain Loss 0 -50 -100 -100 -37 No Full Dispersal Net change (% area) 50 Gain Photo: A. Vliegenthart 0 2. DRIVERS OF CHANGE OF POLLINATORS, POLLINATION NETWORKS AND POLLINATION -50 -67 -50 -42 Loss -100 -98 No Full Dispersal Loss -100 -91 No Full Dispersal • More widespread species • High losses under “no dispersal” Bombus zonatus Category: HR Photo: G. Holmström Apatura metis Category: HHR Photo: M. Wiemers • Gains under “full dispersal” Net change (% area) 50 Gain +24 0 Net change (% area) 50 Gain +38 0 -50 -50 Loss -100 -84 No Full Dispersal Loss -100 -90 No Full Dispersal Lost distribution (becomes climatically unsuitable for species by 2080/2100) Stable distribution (remaining climatically suitable area by 2080/2100) Gained distribution under “full dispersal” assumption (become climatically suitable by 2080/2100)
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The assessment report on POLLINATOR
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FOREWORD The objective of the Inter
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THE ASSESSMENT REPORT ON POLLINATOR
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150 THE ASSESSMENT REPORT ON POLLIN
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THE METHODOLOGICAL ASSESSMENT OF SC
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478 ANNEXES
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POLLINATORS POLLINATION AND FOOD PRODUCTION

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