Frontiers of Biogeography Advances in conservation biogeography: towards protected area effectiveness under anthropogenic threats

This study endorses the main findings of a PhD thesis (Hoffmann 2020) and the manuscripts included intend to advance the success of protected areas in biodiversity conservation mediated through effective and efficient protected area management. The manuscripts provide missing scientific evaluations that modern conservation planning over large geographical extents requires: the comprehensive quantification of species diversity within and between protected areas; the development and application of efficient and effective in-situ monitoring and remote sensing of species diversity; and the assessment of anthropogenic climate change threats to protected areas. Moreover, the manuscripts aim at spreading conservation-minded data and knowledge by means of publishing open-access papers, open-source software and open data. This thesis synopsis is to stimulate a growing scientific and public debate on the effectiveness of protected areas and nature conservation under anthropogenic threats, which is necessary to stop nature’s decline and thus guarantee a sustainable future for the welfare of generations to come. dissimilarity (Dissimilarity_Total) indicates beta diversity between protected areas regarding their species composition. e) Balanced dissimilarity (Dissimilarity_Balanced) and f) gradient dissimilarity (Dissimilarity_Gradient) are the additive components of total dissimilarity (Baselga 2013). For details see Hoffmann et al. (2018).

• I offer new insights and tools on how to monitor species diversity efficiently in the field and by remote sensing, and support the conservation movement by open-access publications, open-source software and open data.
• Perspectives are given on a global protected area management system and the next generation of conservation biogeographers.
Keywords: nature reserves, species diversity, ecosystem functioning, ecosystem services, climate change, monitoring, remote sensing

Motivation
We are currently in the midst of the sixth mass extinction event in earth history (Ceballos et al. 2015). This crisis is outstanding as the causes are not natural, such as asteroid collisions or volcanism, but the human species. About 1 million species are threatened with extinction at present and extinction rates are increasing (Díaz et al. 2019). The main drivers of this unprecedented biodiversity loss are human land use, exploitation of natural resources and organisms, anthropogenic climate change, environmental pollution and invasive species. The decline of nature is likely to continue in the near future because the driving forces result from powerful capitalistic systems and the consumptive needs of a growing human population striving after an increasing standard of living in a globalised world (Pereira et al. 2010, Díaz et al. 2019. A dilemma evolves as human well-being depends on the protection of nature's integrity (Cardinale et al. 2012). We benefit from ecosystem functioning, goods and services, which build on biodiversity (Tilman et al. 2014). In addition, species have the right to exist independent of their benefits to humans (Wilson and Peter 1988). The use and existence values of nature are reasons for nature conservation and motivate me as a conservation biogeographer.
I refer to conservation biogeography as 'the application of biogeographical principles, theories, and analyses, being those concerned with the distributional dynamics of taxa individually and collectively, to problems concerning the conservation of biodiversity' (Whittaker et al. 2005). Conservation biogeography combines the research disciplines of conservation biology and biogeography. Conservation biogeography has evolved from conservation biology but is deeply rooted in biogeography, which emerged as a distinct discipline as early as in the 19th century (Whittaker and Ladle 2011). Alexander von Humboldt was the first biogeographer who raised concerns about the human impacts on nature (von Humboldt 1845).
Conservation biogeography puts biodiversity into large spatial contexts. The mapping and modelling of species diversity of conservation concern over large geographical extents and over time lie at the core of conservation biogeography (Lomolino and Heaney 2004). The original agenda of conservation biogeography is to generate knowledge on how to optimise the conservation of biodiversity in space and time. Nowadays conservation biogeographers are facing manifold roles to stop the accelerating loss of biodiversity: they do not only generate the knowledge about biodiversity conservation in a geographical context but also implement, manage, monitor and adapt conservation initiatives in close cooperation and communication with stakeholders, such as policy-makers, managers, businesses, governmental and nongovernmental organisations, local people and the general public.
Effective instruments for biodiversity conservation are protected areas (Watson et al. 2014). Protected areas are expected to be the only effective and efficient conservation tools in the future because a high degree of biodiversity will hardly be able to persist in the increasingly human-dominated landscapes of the Anthropocene (Watson et al. 2016). A proliferating number of conservationists propose setting aside half of terrestrial earth as protected areas, to compensate for the current loss of biodiversity and save our planet (Wilson 2016). The significance of protected areas for global biodiversity conservation is also reflected in the Aichi Biodiversity Targets, which is a set of 20 global targets under the Strategic Plan for Biodiversity 2011-2020, adopted by the signatories of the Convention on Biological Diversity (CBD) in

Synthesis
In conservation biogeography, the multiple roles of protected areas are studied, which aim at preserving values and objectives of nature (Ladle and Whittaker 2011a). The success that protected areas had during the 21st century (Watson et al. 2014, Bingham et al. 2019) is threatened, primarily by human land use (Schulze et al. 2018) and climate change (Hannah 2008, Peters and Darling 1985, Gross et al. 2017, Thomas and Gillingham 2015, Araújo et al. 2011. Threats to biodiversity are occurring globally (Díaz et al. 2019) and biodiversity is rapidly lost (Pimm et al. 2014). Consequently, protected area planning and management has not only to become more effective and efficient, but also needs to consider local to global scales to ensure biodiversity conservation worldwide. In the following, I explain how each manuscript can advance effectiveness and efficiency of protected areas in preserving biodiversity at the local to global extent (Table 1).

Quantifying species diversity within and between protected areas of a continental estate
The scientific prerequisites of successful management are the research and monitoring of management effectiveness, i.e. the degree to which conservation targets are met by protected area management (Hockings et al. 2006). Species diversity is a reasonable indicator of protected area management effectiveness (Le Saout et al. 2013). However, species diversity is not entirely known inside many protected areas, because management resources are limited and thereby only priority species are considered in conservation measures. In Hoffmann et al. (2018), we accordingly analysed the current distributions of priority species within major protected areas in the EU. The study includes 1303 species in ten taxa. These priority species are listed in the annexes of the Birds and Habitats directives, the two most important policies for species conservation in the EU. Member states are obliged to periodically report the occurrence of those focal species. We used these occurrence data and merged them with 285 national parks and 147 UNESCO Man and Biosphere (MAB) reserves, which are two major protected area designations focusing on species conservation. We then applied a novel, multifunctional approach to calculate different metrics of conservation value that represent different components of species diversity, involving inventory diversity, deviation from the species-area relationship, species rarity and differentiation diversity. We offer this approach to evaluate how much biodiversity is found inside protected areas (i.e. protected areas' representativeness), which can be used to enhance protected area management effectiveness, e.g. by trying to preserve more or more diverse species. We show that individual protected areas significantly vary in their species diversity, which is often not associated with protected area size ( Fig. 1).
Protected areas at the margins of EU territory harbour only few species but are key to conserving rare species. This analysis allows a multi-facetted and more accurate estimation of This study highlights the present conservation value of renowned European protected areas in terms of species diversity. It informs protected area management from a local to continental perspective.

Using remote sensing for efficient monitoring of species diversity
In the face of the high rates of current biodiversity loss (Díaz et al. 2019, Ceballos et al. 2015, Barnosky et al. 2011, Pimm et al. 2014, the monitoring of the biotic and abiotic environment needs to become time and cost-efficient. Remote sensing is a growing, time-and cost-efficient tool for conservation (Horning et al. 2010, Turner et al. 2015, Rocchini et al. 2019). In the biodiversity conservation context, remote sensing techniques have been primarily used to estimate plant species richness and abundance (i.e. alpha diversity), whereas the assessment of differentiation diversity (i.e. beta diversity) has been neglected, even though beta diversity is crucial for conservation planning (Socolar et al. 2016). Therefore, one article of the synopsis contributed to the analysis of beta diversity using remote sensing techniques. In images. Additionally, we surveyed perennial vascular plant species abundances in three predefined community types: succulent scrubland, Pinus canariensis forest and subalpine scrubland. We show that up to 85% of beta diversity is reflected by the remote sensing variables in the wet season (Fig. 2). The LiDAR variables explain less variation of beta diversity than the S2 variables. The explanatory power of S2 variables decreases with increasing grain size, while the explanatory power of LiDAR variables increases. Accordingly, we demonstrate that open remote sensing data are able to accurately reflect plant communities. Such remote sensing approaches, however, need to be complemented by field surveys to reveal the complete variation in community composition.

Optimising field surveys for efficient monitoring of species diversity
In contrast to remote sensing, in-situ surveys are classic approaches to assess species diversity inside protected areas. In-situ sampling procedures can, however, still be improved ( 1948) were calculated for different sizes and quantities of subplots. We simulated larger subplot sizes by unifying adjacent 2 m × 2 m-subplots. Shannon's information entropy was then applied to measure the information content among richness and diversity values resulting from different subplot sizes and quantities. The optimal size and number of subplots is the lowest size and number of subplots returning maximal information. We found that the information content among richness values increases with subplot size which is not related to the number of subplots ( Fig. 3). Subsequently, the largest subplot size available is the optimal size for information about richness. We also show that information content among diversity values increases with subplot size when 18 or less subplots have been considered, and decreases when at least 27 subplots have been surveyed. Therefore, the subplot quantity determines whether the smallest or largest subplot size available is the optimal size, and whether the optimal size can be generalised across both, species richness and diversity. Given a 2 m × 2 m size, we estimated an optimal quantity of 54. Given a size of 4 m × 4 m, we estimated an optimal number of 36.
The optimal number of plots can be generalised across both indices because it barely differed between the indices given a fixed subplot size. Effective and efficient in-situ sampling designs can be created with this approach.  (Batllori et al. 2017, Gonzalez et al. 2018 or Europe (Nila et al. 2019, Barredo et al. 2016, Araújo et al. 2011. A spatially high-resolution assessment of local climate change impacts inside protected areas worldwide is required to guide local protected area management towards global conservation goals (Felton et al. 2009). Loarie and colleagues provide such an assessment, but that is restricted to temperature change (Loarie et al. 2009). A global assessment of the local climate change impacts on protected areas is missing but essential to guide local protected area management towards global conservation goals. Hoffmann et al. Species loss within protected areas is rarely compensated for by incoming taxa (Burns et al. 2003, Coetzee et al. 2009, Araújo et al. 2011, Fuentes-Castillo et al. 2019. We found that protected areas in the temperate and northern high-latitude biomes experience especially high proportions of climate conditions that are predicted to be novel within the protected area network in a local, regional and global context by the year 2070 (Fig. 4). By relating characteristics of protected area design to the predicted climate shifts, we could estimate the future impacts of anthropogenic climate change on the performance of protected areas in biodiversity conservation. Small protected areas of temperate biomes in lowland regions with low environmental heterogeneity and high human pressure but low irreplaceability for threatened species will lose especially high proportions of their currently protected climates.
This analysis directs adaptation measures towards protected areas that are strongly affected by climate change, of low adaptation capacity and of high conservation value.

Towards a global protected area management system
Protected areas offer solutions to the sixth mass extinction event in earth history and are preferred conservation policies given climate change (Hagerman and Satterfield 2014). Aichi Biodiversity Target 11 sets a terrestrial protected area coverage of 17% as a conservation target, but protected area extent does not indicate protected area effectiveness (Kati et al. 2015, Barr et al. 2011, Joppa and Pfaff 2009, Visconti et al. 2019, Rodrigues et al. 2004. For that reason, a certain degree of management effectiveness of the global protected area estate should become a legally binding global conservation target as well.
The aim of this study is to stimulate coordinated biodiversity conservation through protected areas at the national and international level, by providing information about biodiversity and threats within individual protected areas of continental to global networks.
Each manuscript of this thesis contributes to biodiversity conservation in a specific way.
However, a comprehensive analysis that reveals the complex relationships between nature's various values, conservation objectives and threats inside the global protected area estate has not been realised yet. This is a main future, albeit ambitious, perspective in conservation  (Reyers et al. 2017). The definition of essential variables has led to advances in data collection, storage, distribution and use (Kissling et al. 2015) that are essential to big data analyses. Remote sensing (Pettorelli et al. 2016) and long-term ecological research stations (Haase et al. 2018)  Biodiversity Target 11, and SDG 14 and 15. Therefore, the DOPA is already providing a scientific foundation for a globally coordinated management system for protected areas. I consider the development and application of such a global protected area management system as a crucial future task for conservation biogeographers, to reach the global biodiversity and sustainability goals.

Next generation conservation biogeography
Conservation biogeography is advancing the effectiveness of protected areas but faces many future challenges that are not related to protected areas. Filling biogeographical knowledge gaps and improving biodiversity forecasts are persistent scientific challenges. Turning theory into practice, educating, communicating and changing social values and lifestyles are common practical challenges. Accepting these challenges, conservation biogeographers need to focus on large geographical extents but small grain because threats to nature are occurring locally all over the world (Alagador 2020). Global conservation problems beyond 2020 can only be solved by local conservation strategies that are globally coordinated via international collaboration (Mace et al. 2018).
Conservation research is restricted by the unavailability of data. Growing conservation knowledge evolves from an increasing quality and quantity of data (Wüest et al. 2019).
Conservation biogeographers work on the Linnean, Wallacean and extinction estimate shortfalls by collecting new data (Ladle and Whittaker 2011b). However, temporal and financial resources for collecting data and monitoring are limited. Hence, sampling and monitoring techniques need optimisation to become less time-consuming and costly. Open information systems, data repositories, databases and data sets play a central role to foster global conservation research by the coming generations of conservation biogeographers. Varying quality, bias, noise and uncertainty within data require meta-data in order to efficiently harvest and analyse the data (Wohner et al. 2019, Wüest et al. 2019. Open-source software advances data analyses, their documentation, transparency and reproduction. Furthermore, citizen science is a promising tool to enhance data collection, monitoring and analysis by participating citizens.
Citizen science brings the scientific community and the public together, which supports public education and nature conservation at the same time (Devictor et al. 2010, Sullivan et al. 2014. However, the increasing availability of data should not prevent anyone collecting new, high-quality data, especially in time of rapid environmental changes. More scientists need to be trained to enhance the quality and quantity of available data and methods in the future. Predictions are to some degree uncertain and uncertainty may prevent decision-makers from acting (Gray 2011, Bagchi et al. 2013, Wang et al. 2012, Millar et al. 2007, Pacifici et al. 2015, Conroy et al. 2011, Hallegatte 2009, Belote et al. 2018). There are, nevertheless, approaches to decision-making in the conservation context that account for model uncertainties (Polasky et al. 2011, Hoekstra 2012, Hayes et al. 2013, Yousefpour and Hanewinkel 2016. A future challenge is to minimise the uncertainties of model predictions, e.g. by probabilistic analyses (Billionnet 2015, considering past dynamics (Di Marco et al. 2015), using sensitivity analysis and null-models (Feeley and Silman 2010), and incorporating as many relevant hypotheses, data and models as possible , Conroy et al. 2011. Forecasts are improved by refined theories as well as by the consideration of scale-dependency, inadequacies of input data and sensitivity of projections to model structure and parameterisation (Whittaker et al. 2005, Araújo andNew 2007). However, in contrast to meteorologists, ecologists still miss a comprehensive theory to sufficiently predict complex ecosystem assemblies (Higgins 2017), which would promote the human ability to safeguard nature.
In the view of the current rates of nature's declines, another important task for conservation biogeographers is to work harder on improving the communication and collaboration between stakeholders, such as scientists, policy-makers, managers and people (Costello et al. 2015). Publishing open-access is a substantial first step to communicate research efficiently. Nature conservation is a value-laden field, which can complicate communication.
Studies have shown that effective conservation policy and management is based on well communicated, explained and contextualised research (Kalliola et al. 2008, Manfredo et al. 2016, Morrison 2016. Therefore, researchers need to translate their findings into a plain language that stakeholders understand. If stakeholders recognise that their well-being depends on nature conservation, they may be willing to support conservation. Using social media is an efficient way of communicating science, though not without pitfalls (Bombaci et al. 2016). In contrast, academic media do not reach the majority of people (Knuth and Jacobson 2000) and traditional media tend to be prone to polarisation that threatens the credibility of research.
Scientists can even apply marketing techniques to reach the majority of people (Wright et al. 2015, Redford et al. 2015. Knowledge from social-psychological science helps to mainstream Protected areas decrease habitat degradation (Geldmann et al. 2013, Joppa andPfaff 2010) and maintain species and populations better than other conservation measures (Geldmann et al. 2013, Karanth et al. 2009, Taylor et al. 2011, Laurance et al. 2012, Walston et al. 2010, Hilborn et al. 2006. Biodiversity is higher inside protected areas than in their surroundings resources (Postel and Thompson 2005, Palomo et al. 2013, Xu et al. 2017, tourism and recreation (Balmford et al. 2009) and poverty reduction (Andam et al. 2010). Moreover, the global protected area estate expands (Bingham et al. 2019).
If the global protected area extent grew to half of the terrestrial area on earth, new protected areas would have to be wisely planned to stop biodiversity loss (Pimm et al. 2018, Montesino Pouzols et al. 2014) and meet human demands simultaneously (Ellis and Mehrabi 2019). Protected area expansion is, however, challenging because land is increasingly modified and used for human purposes only (Sala 2000), which emphasises the need for nature conservation outside protected areas. A high degree of biodiversity can exist outside protected areas. Some species are even restricted to unprotected areas (Rodrigues et al. 2004), e.g. in Canada (Deguise and Kerr 2006) and in the Mediterranean biome (Cox and Underwood 2011).
Species migrating between protected areas also depend on unprotected areas (Troupin and Carmel 2014). Furthermore, established protected areas are often taken as justification for environmental degradation in the protected area surroundings (McNeely et al. 1990, Radeloff et al. 2010, Hellwig et al. 2019). If biodiversity is lost outside protected areas, this will have, in turn, consequences for the biodiversity inside (Laurance et al. 2012, Rada et al. 2019). The smaller a protected area is, the more it is affected by unprotected surroundings (Yamaura et al. 2008). Consequently, nature conservation outside protected areas is essential as well.
The sustainable use of unprotected land can complement protected areas in conserving biodiversity (Locke et al. 2019), e.g. by applying low-intensity agriculture and forestry (Kremen and Merenlender 2018). Land sharing (i.e. sharing agricultural land with conservation efforts) and land sparing (i.e. temporally sparing agricultural land for conservation) are two strategies to merge agricultural practices and biodiversity conservation in cultural landscapes (Baudron and Giller 2014). Private land can also be dedicated to biodiversity conservation by voluntary conservation efforts, e.g. in private gardens (Farmer et al. 2017). Such efforts refer to other effective area-based conservation measures (OECMs), which are essential complements to protected areas for reaching global conservation targets (Dudley et al. 2018, Frascaroli et al. 2019).
There are numerous signs of general conservation success. Conservation efforts have, for instance, decreased the extinction risk of mammals and birds in 109 countries by 29% from 1996 to 2008 (IPBES 2019); the average extinction risk of birds, mammals and amphibians would have been at least 20% higher without conservation initiatives; more than 107 highly threatened birds, mammals and reptiles took profit from the conservation-minded eradication of invasive mammals on islands. Many endangered species are recovering (IUCN 2019).
Moreover, many people do perceive nature conservation as a priority (Varma et al. 2015).
Public media and institutions such as zoos, museums and botanical gardens, increasingly provide conservation-minded education programmes (Miller et al. 2004). Markets for green and sustainable products have been growing enormously (Steinemann et al. 2017). The economic value of nature is more often incorporated into economics and policy, which supports nature conservation (Reyers et al. 2013, Kubiszewski et al. 2013, Bateman et al. 2013, Waldron et al. 2017). Policy-makers increasingly discontinue perverse subsidies to environmentally harmful businesses (Merckx and Pereira 2015). The members of the European Parliament call for legally binding biodiversity targets, equivalent to the Paris agreement on climate change (European