Sac/2018/09/05 Scottish Natural Heritage Scientific
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SAC/2018/09/05 SCOTTISH NATURAL HERITAGE SCIENTIFIC ADVISORY COMMITTEE SNH TERRESTRIAL INVERTEBRATE STRATEGY Purpose 1. This paper and the Annex outline an initial draft SNH conservation strategy for Scotland’s terrestrial invertebrates. The approach focuses on species of conservation concern for which viable, relevant and evidence-based measures are available. The level of ambition and proposed actions area provisional subject to wider consultation. This proposal is contribution to the Scottish Biodiversity Strategy. Action 2. The Scientific Advisory Committee is asked to: i) Review the rationale of this strategy; and ii) Endorse approach taken. Preparation 3. This paper was prepared by Athayde Tonhasca, with input from Mairi Cole, Iain MacGowan and Des Thompson. It also benefited from discussions with representatives of Buglife (The Invertebrate Conservation Trust), RSPB, Bumblebee Conservation Trust, Cairngorms National Park Authority, RSPB, James Hutton Institute, British Arachnological Society, Butterfly Conservation Scotland, British Dragonfly Society and Scotland's Rural College. The paper is sponsored by Sally Thomas. Background 4. Scotland is the home of at least 24,000 invertebrate species (more than 12 times the number of all UK bird, mammal and vascular plant species combined). Many of these, particularly in montane, upland and boreal habitats, have become rare or extinct elsewhere in the UK or Europe (Rotheray & MacGowan, 1996; Macadam & Rotheray, 2009). Habitat loss and fragmentation, land conversion, agricultural intensification, landscape homogenisation, urbanization, pesticides and pollution have been identified as the main threats to invertebrate species in Scotland and elsewhere (Macadam & Rotheray, 2009; Aspinall et al., 2011). Recently, climate change has been recognised as one of the main long-term threats to biodiversity. There is limited evidence that climate changes are causing declines in the abundance of some species, although observations are site- or habitat-specific and generally in upland areas. Climate change may also have significant indirect effects: phenological events are happening earlier for several species groups (Parmesan, 2007). Such asynchrony could alter interactions between plants, herbivores, predators and pollinators (Bartomeus et al., 2013) 1 SAC/2018/09/05 and may lead, for example, to segregation between plants and pollinators, and between food plants and phytophagous species (Willmer, 2012). 5. This proposal sets out a conservation strategy for terrestrial invertebrates. It covers four of the five strategic goals included in the Aichi Targets and the European Union's Biodiversity Strategy: 1. Address the causes of biodiversity loss; 2. Reduce the direct pressure on biodiversity and promote sustainable use; 3. Safeguard ecosystems, species and genetic diversity; and 4. Participatory planning, capacity building (by targeting biodiversity values, functioning, status and trends). This strategy also complements other initiatives such as SNH's Species Decision Tool, the Pollinator Strategy for Scotland, and the Climate Change Strategy (Climate change and nature in Scotland 2012). Moreover, it underpins the protection established by law, e.g., Directive 92/43/EEC on the Conservation of Natural Habitats and of Wild Fauna and Flora, the Wildlife and Countryside Act 1981, Conservation Regulations 1994 and The Nature Conservation (Scotland) Act 2004. Approach 6. A UK list of priority species for conservation was developed under the UK Biodiversity Action Plan (UK BAP) in 1994, which was revised and updated by JNCC and Defra (UK Post-2010 Biodiversity Framework) on behalf of all four UK governments (the Four Countries' Biodiversity Group). The UK list of priority species served as the basis for the current statutory framework for biodiversity conservation in Scotland, the Scottish Biodiversity List. From this list, the terrestrial invertebrates with greatest need of conservation action were identified according to following criteria: Threat. This criterion is centred on IUCN's (2012) categories Vulnerable, Endangered and Critically Endangered, and on the older British Red Data Book's (RDB) categories Endangered (RDB1), Vulnerable (RDB2) and Rare (RDB3). The IUCN criteria for threat focus on perceived danger of extinction. However, due to the scarcity of data for the overwhelmingly majority of invertebrates, most of the relatively few IUCN assessments of threat are limited to information on geographic range (Cardoso et al., 2011). The RDB categories are also based on geographic distribution, namely area of occupancy (number of 10-km squares), without taking into account trends for increase or decline. This focus on a single variable, i.e., distribution, to assess threat is not too problematic because range is broadly correlated with population size for many plant and animal groups (Lawton, 1993; Brown, 1995; He & Gaston, 2000). Endemism. Endemic species are confined to a certain region or have a relatively limited distribution, therefore they are highly adapted to their home range. Since endemic species are restricted to particular areas, they are intrinsically susceptible to extinction because any environmental disturbance could decrease their numbers to dangerous levels or wipe them out entirely. Endemic species are often considered indicators or surrogates of biodiversity and the focus for the conservation. Endemism, combined with rarity in its different forms (Rabinowitz et al., 1986), are the factors that confer the greatest risk of extinction (Myers et al., 2000; Gaston, 2003). 2 SAC/2018/09/05 Endemic species are of high priority because Scotland has the sole responsibility for their protection: this is an international duty of care, because if endemic species become extinct in Scotland, the world's biodiversity becomes poorer. Relevance. Size and importance of Scottish populations within GB. Knowledge. Realistic conservation measures are only possible when there is sufficient information about the species' biology, ecology, and management requirements. 7. Based on the above conditions, species were classified according to the following hierarchical categories of priority: 1. Endemic species (in Scotland or GB) known or believed to be under threat or vulnerable. 2. Species with a significant proportion of their GB population in Scotland (near endemics) that are known or believed to be threatened or vulnerable, and for which management measures or risk factors are known. 3. Species known or believed to be threatened or vulnerable and for which management measures or risk factors are known. In most cases we have reasonably understanding of species' biology, ecology, distribution, and conservation history. 4. Species of conservation concern but whose occurrence in Scotland is doubtful; species of conservation concern for which there is insufficient information, i.e., monitoring and research are the only realistic options available; species that are intrinsically vulnerable but do not require immediate action. Output 8. This screening identified 179 species of priority levels 1 to 4. These are mostly endemics, species under threat or vulnerable, species with significant populations in Scotland, and species for which management measures are available. Proposed actions 9. Actions aimed at species on restricted sites. A few priority species have well- defined and relatively restricted distributions, which range from a single site to a few locations within the same geographical area. These species are intrinsically at risk of local extinctions because they are particularly vulnerable to stochastic factors such as fire, floods, severe weather, etc. For these cases, conservation practices can be detailed and tailored. There are ongoing measures for some of these species, but their safeguard requires long-time commitments. 10. Actions aimed at habitats. For the majority of terrestrial invertebrates, broad habitat management practices are the most pragmatic conservation options available because the species are widely distributed, or our understanding of their ecological requirements is limited. Moreover, it is reasonable to assume that populations are secure as long as their habitats are in a 'steady state' (at least 3 SAC/2018/09/05 within a reasonable period of time; all habitats eventually evolve - as for example in response to climate change). Therefore habitat management and assessment may turn out to be the best options. Habitat quality may also be used as a proxy to conservation status of species and assemblages in cases of logistical constraints, e.g., insufficient resources, or unavailability of entomological expertise. 11. Climate change actions. Changes in phenology have proven to be some of the most conspicuous reactions by wildlife in response to recent climatic warming (Walther, 2010), although almost nothing is known about long-term population- level effects of population shifts and phenology. However, our understanding of the processes involved is poor and therefore the magnitude of climate-induced effects cannot currently be predicted. The best course of action is to monitor the priority species more likely to be susceptible, and increase our knowledge about their biology and ecology. Actions for species likely to respond to climate change address three of the eight adaptation principles in SNH' Corporate Plan Climate change and nature in Scotland: reduce pressures on habitats and species, improve habitat management, and consider translocation of species. 12. Survey.