3D-imaging technologies provide measurements of terrestrial and aquatic ecosystems' structure, key for biodiversity studies. However, the practical use of these observations globally faces practical challenges. Firstly, available 3D data are geographical biased, with significant gaps in the tropics. Secondly, no data source provides, by itself, global coverage at a suitable temporal recurrence. Thus, global monitoring initiatives, such as assessment of essential biodiversity variables (EBVs), will necessarily have to involve the combination of disparate datasets. We propose a standardised framework of ecosystem morphological traitsheight, cover and structural complexitythat could enable monitoring of globally-consistent EBVs at regional scales, by flexibly integrating different information sourcessatellites, aircrafts, drones or ground data -, allowing global biodiversity targets relating to ecosystem structure to be monitored and regularly reported.

Summary1. Habitat structure is important in explaining species diversity patterns for many animal groups. If we could map habitat structure over large spatial scales, we could use habitat structure-species diversity (HS-SD) relationships to model species diversity and inform conservation planning and management. Traditional approaches for measuring habitat structure cannot be applied over entire landscapes, but remote sensing tools are now able to overcome this limitation. Here, we explore the potential of airborne lidar for the assessment and monitoring of animal species diversity in terrestrial environments. 2. We review the habitat attributes commonly recorded in the study of HS-SD relationships and the spatial scale of their measurement, in papers published between 1960 and 2013. We also gather evidence for the use of lidar to make relevant measurements at similar scales. 3. Eight out of 15 attributes of habitat structure commonly used in published studies relate to the vertical dimension of habitat. The core strength of lidar is that it is a vertical profiler, and this technology can be used to derive estimates of all but one of these structural attributes. Lidar can also be used to improve the measurement of the four commonly used attributes focusing on the horizontal heterogeneity of habitat patches. The spatial grain and extent of HS-SD studies is usually within the operational capability of airborne lidar; when a vertical measure of habitat structure has been employed, this is true in 84% of published studies. The potential efficacy of lidar in this field of biodiversity studies is underlined by several published examples of lidar modelling of animal species diversity. 4. We conclude that lidar remote sensing is fit for the purpose of biodiversity assessment and monitoring through its ability to characterize habitat structure, a key driver of animal species diversity, over large spatial scales. We advocate wider application of lidar-based HS-SD indicators to help tackle the current biodiversity crisis. In combination with other remote sensing products, these indicators may support the implementation and monitoring of environmental legislation, inform gap analyses and the planning of management actions for protected areas and species, and drive greater synergy with forest-based climate change mitigation.

Airborne lidar is a remote-sensing tool of increasing importance in ecological and conservation research due to its ability to characterize three-dimensional vegetation structure. If different aspects of plant species diversity and composition can be related to vegetation structure, landscape-level assessments of plant communities may be possible. We examined this possibility for Mediterranean oak forests in southern Portugal, which are rich in biological diversity but also threatened. We compared data from a discrete, first-and-last return lidar data set collected for 31 plots of cork oak (Quercus suber) and Algerian oak (Quercus canariensis) forest with field data to test whether lidar can be used to predict the vertical structure of vegetation, diversity of plant species, and community type. Lidar- and field-measured structural data were significantly correlated (up to r= 0.85). Diversity of forest species was significantly associated with lidar-measured vegetation height (R(2) = 0.50, p < 0.001). Clustering and ordination of the species data pointed to the presence of 2 main forest classes that could be discriminated with an accuracy of 89% on the basis of lidar data. Lidar can be applied widely for mapping of habitat and assessments of habitat condition (e.g., in support of the European Species and Habitats Directive [92/43/EEC]). However, particular attention needs to be paid to issues of survey design: density of lidar points and geospatial accuracy of ground-truthing and its timing relative to acquisition of lidar data.

SummaryMost range shift predictions focus on the dispersal phase of the colonization process. Because moving populations experience increasingly dissimilar nonclimatic environmental conditions as they track climate warming, it is also critical to test how individuals originating from contrasting thermal environments can establish in nonlocal sites.We assess the intraspecific variation in growth responses to nonlocal soils by planting a widespread grass of deciduous forests (Milium effusum) into an experimental common garden using combinations of seeds and soil sampled in 22 sites across its distributional range, and reflecting movement scenarios of up to 1600 km. Furthermore, to determine temperature and forest-structural effects, the plants and soils were experimentally warmed and shaded.We found significantly positive effects of the difference between the temperature of the sites of seed and soil collection on growth and seedling emergence rates. Migrant plants might thus encounter increasingly favourable soil conditions while tracking the isotherms towards currently 'colder' soils. These effects persisted under experimental warming. Rising temperatures and light availability generally enhanced plant performance.Our results suggest that abiotic and biotic soil characteristics can shape climate changedriven plant movements by affecting growth of nonlocal migrants, a mechanism which should be integrated into predictions of future range shifts.

Mediterranean forests have always had to cope with challenging environmental conditions that change across different temporal and spatial scales. However, the rapidity of current environmental change, driven by greater-than-ever human influences on natural processes, is unprecedented and has triggered renewed research endeavour into the impacts on Mediterranean ecosystems (Valladares 2008). The climate of Mediterranean areas is expected to become drier and warmer, with decreasing water availability for plants and increasing evapotranspiration (IPCC 2007). This will result in more acute physiological stress, increased importance of species-specific tolerances, plasticity and thresholds, phenological change and recruitment effects (Montserrat-Martín et al. 2009; Morin et al. 2010; Peñ uelas et al. 2004). Several studies have demonstrated how the conditions currently experienced by seedlings and saplings are quite different to those when current adults recruited (Lloret & Siscart 1995; Montoya 1995). The anticipated impacts of such changes have led to a renewed interest in classic ecophysiological research into drought stress and tolerance (Wikelskia & Cooke 2006), as well as population-level studies on phenotypic plasticity and the evolution of tolerance in certain key tree species, such as Holm (Quercus ilex) and cork oaks (Q. suber) (Gimeno et al. 2009; Ramírez-Valiente et al. 2010).

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Global forest assessments use forest area as an indicator of biodiversity status, which may mask below-canopy pressures driving forest biodiversity loss and ‘empty forest’ syndrome. The status of forest biodiversity is important not only for species conservation but also because species loss can have consequences for forest health and carbon storage. We aimed to develop a global indicator of forest specialist vertebrate populations to improve assessments of forest biodiversity status. Using the Living Planet Index methodology, we developed a weighted composite Forest Specialist Index for the period 1970–2014. We then investigated potential correlates of forest vertebrate population change. We analysed the relationship between the average rate of change of forest vertebrate populations and satellite-derived tree cover trends, as well as other pressures. On average, forest vertebrate populations declined by 53% between 1970 and 2014. We found little evidence of a consistent global effect of tree cover change on forest vertebrate populations, but a significant negative effect of exploitation threat on forest specialists. In conclusion, we found that the forest area is a poor indicator of forest biodiversity status. For forest biodiversity to recover, conservation management needs to be informed by monitoring all threats to vertebrates, including those below the canopy.

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