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The extent of protected-area (PA) networks is widely used as an indicator of progress toward agreed biodiversity targets. According to this indicator, conservation trends are positive and promising. Yet, despite significant protection efforts and financial resources invested, biodiversity continues to decline (Butchart et al., 2010) and threats are ever-growing. It is therefore vital to understand what is the actual contribution of the PA network toward achieving conservation goals.

However, we know rather little about the effectiveness of PA networks. Effectiveness is not trivial to measure, and it has many components. We are interested in how well biodiversity features are covered by PAs, how well they persist within the network, and whether PAs are able to stop or at least reduce major threats within their borders. To date, only coverage has received substantial attention, in studies similar to that by D'Amen et al. (2013). Across scales, from global to local (e.g. Rodrigues et al., 2004) the message is similar: PAs are not representative enough, and coverage gaps are often substantial. Such coverage studies have predominantly focused on plants and vertebrates, with only a handful of examples for invertebrates. D'Amen et al. (2013), by focusing on the coverage of saproxylic beetles by Italian PAs, present an important case. They found that a good fraction of saproxylic beetle species of conservation concern is poorly covered by the national network of PAs or by the larger Natura 2000 network. Furthermore, they found that only national PAs, but not Natura 2000, include more sites that are irreplaceable (or essential) for saproxylic beetle conservation than a random set of sites. This result is perhaps not so surprising, as Natura2000 sites are frequently set to cover species that largely depend on traditional land-use. This is also because the Natura 2000 network was established across the European Union with the aim to conserve biodiversity, while at the same time ensuring the sustainability of human activities. More than half of the Member States undertake agricultural and forestry activities in over 60% of their Natura 2000 sites (Tsiafouli et al., 2013), which translates into less coverage of the types of habitats that saproxylic beetles depend on: forested areas, with mature trees and decaying wood.

In addition to poor coverage of species, perhaps more worrisome is the fact that we do not know much about other components of effectiveness, or for instance, if the covered species will be able to persist within PAs. Are the threats reduced in PAs? Do protected habitats remain suitable for focal species through time? Are PAs large enough, connected enough? PAs should safeguard the long-term persistence of biodiversity, and yet little is known about the persistence of species or the retention of condition in PAs at large. The lack of temporal data required for such assessments is daunting, yet the few available studies, which have focused on vertebrates or plants, are rather discouraging (e.g. Laurance et al., 2012).

European PAs, in particular, face important challenges in their efforts to maintain biodiversity into the future (see Gaston et al., 2008). Most PAs in Europe are small and isolated, and this is especially true for Natura 2000 sites, where some of the pressures for habitat transformation continue. Such sites in isolation cannot sustain the populations sizes required for long-term viability (Traill, Bradshaw & Brook, 2007). Additionally, climate change evidence has raised awareness of the fact that what is covered in PAs is not static. PAs have already experienced some changes attributable to climate change (Thomas et al., 2012), and projections for Natura 2000 areas are rather alarming (Araújo et al., 2011). Assessments of current species representation in PAs, such as the one of D'Amen et al. (2013), can lead to misleading conclusions of species' conservation status if they disregard the ongoing and near-future impacts of climate change. For instance, Kujala et al. (2011) have shown that because of the particular distribution of Finnish PAs, those species that are best represented are also those with declining population trends and projected to contract under a future changing climate. Coverage assessments based on snapshots of occurrence data fail to identify such temporal trends and time lags. Time lags are particularly important when addressing occurrence patterns in small and isolated PAs, as current species occurrence may only reflect much greater habitat availability in the past. Such extinction debt (e.g. Kuussaari et al., 2009) would go unnoticed in common coverage assessments.

Goals of the global 2011–2020 Biodiversity Strategic Plan, and in particular Aichi target 11, require the expansion of the PA network to cover at least 17% of the terrestrial surface. Discussions about how to prioritize areas, where, how large and for what taxa, are timely and necessary. All aspects of PA effectiveness should contribute to the planning of these expansions. Efforts, such as that of D'Amen et al. (2013), to bring invertebrates into this discussion are indispensable: invertebrates dominate in richness and abundance, and often also in biomass. They are of high importance for humankind as they perform essential ecosystem functions. They show similar or even higher extinction rates and/or proportions of threatened species than vertebrate groups such as birds and mammals (McKinney, 1999). Yet, conservation research and policy often neglects them, and only a small fraction of described arthropods is assessed in the Red List of Threatened Species (Zamin et al., 2010). Financial support given to invertebrate conservation is largely inadequate: in Europe, conservation funding obtained through the LIFE–Nature program allocates on average 1000 times less funding to each arthropod species than to vertebrate species (Cardoso et al., 2011). And while many impediments to improving insect conservation relate to socio-political dilemmas, others are due to scientific shortfalls or gaps in knowledge (Cardoso et al., 2011), including undescribed species and poorly known distributions. D'Amen et al. (2013) are able to provide an assessment of the coverage of an invertebrate group, saproxylic beetles, because substantial understanding and spatial data exist for this group in Italy.

Conservation needs are larger than what conservation budgets or international commitments can cater for. And despite the intrinsic value of all biodiversity assets, choices need to be made when conservation resources are scarce. Whether these choices are based on triage or cost-effectiveness, data availability, or the use of surrogates, and whether trade-offs between coverage and persistence should be considered, are matters that continue being extensively debated. But a stronger presence of invertebrate taxa in these debates should be advocated.

References

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  2. References
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