Kenneth F. Rijsdijk

Islands harbour disproportionately high biodiversity and endemism yet are among the world's most threatened ecosystems. Habitat loss is a major driver of this decline, but its magnitude is difficult to interpret on its own: human-induced loss can only be evaluated relative to the long-term natural variability preceding human arrival. Here, we compare human-induced habitat loss rates (HumHLr) with natural baseline habitat loss rates (BaseHLr) across 43 volcanic oceanic islands spanning eight archipelagos worldwide. HumHLr was estimated since first human arrival using two complementary proxies of natural habitat: island-specific vegetation data (local proxy) and the globally standardised Human Modification Index (global proxy). BaseHLr combined the two dominant long-term natural processes reducing habitat on volcanic islands: sea-level rise since the Last Glacial Maximum (SeaHLr) and Holocene volcanism (VolHLr). Our results indicate that HumHLr exceeded BaseHLr by approximately one order of magnitude on nearly all islands (median ratios: 18.6 global proxy, 15.4 local proxy), and was significantly higher than each baseline component, SeaHLr and VolHLr, under both proxies. Within the baseline, sea-level rise contributed more to habitat loss than volcanism, which was restricted to a few geologically active islands. Overall, these findings show that contemporary habitat loss on islands far outpaces the geological processes that shaped island environments over millennia, providing a reference for assessing extinction risk and prioritising conservation.

The field of biogeography aims to reconcile geological changes with the distribution of biodiversity in space and through time. To this end, we examine how geology and climate have affected the spatio-temporal build-up of avian diversity on New Guinea and surrounding islands with a particular focus on birds-of-paradise. Here, we present a new palaeogeographic framework for the formation of New Guinea and surrounding islands from 35 Ma (mega-annum) to the present. We then use detailed information about sea-level changes and a new dated phylogenetic tree of the birds-of-paradise to elucidate, in a combined integrative approach, how geology and climate changes through time have shaped this group of birds. The new palaeogeographic model also has implications for our understanding of the early evolution of passerine birds and their dispersal out of Australo-Papua, which we discuss here. Using an integrative and iterative interdisciplinary approach that combines geological, climatic and evolutionary data, we elucidate the biogeographical history of species and clades with seemingly enigmatic present-day distributions. We present a new palaeogeographic framework (35-0 Ma) for the formation of Earth’s largest tropical island, New Guinea and some surrounding islands, including the northern Moluccas. We integrate data from the new palaegeographic model with information on sea-level fluctuations to determine emergence history and water barriers in space and through time. We present a new dated tree of the birds-of-paradise (Aves, Paradisaeidae), based on genomic data. Using an iterative approach, we synthesise information from the new palaeogeographic model, sea-level fluctuations and the dated tree to determine the optimal time for colonisation of islands around New Guinea by the birds-of-paradise. We discuss the importance of the presence of extensive landmasses north of Australia (proto-Papua) for passerine dispersal and evolution out of Australia. It is clear that significant insight can be gained in both biology and geology when their mutualistic potential is unlocked through an integrative approach.

Outbreaks of fossorial arvicoline rodents have plagued temperate European farmlands throughout history, causing large-scale crop loss and forming reservoirs for zoonotic pathogens. Industrialisation of agricultural practices has led to an increase of agricultural field sizes in Europe, coinciding with the removal of ecological structural elements (ESE) such as hedgerows, tree lines, and bushes. This has promoted both the probability and the spatial extent of vole outbreaks. Here, we review the role of ESE in farmlands in shaping outbreak dynamics of the fossorial vole across field, landscape and regional scales. ESE play a crucial role in the scale and connectivity of vole habitats, and influence competition and predation. Open landscapes with no or few ESE such as grasslands, perennial crops and pastures, form optimal vole habitats and are linked to multi-annual cycling and outbreaks of fossorial vole populations. Conversely, ESE exert a limiting force on population growth and the likelihood of outbreaks. ESE create physical barriers between vole populations and offer corridors, habitats and perching sites for predators of the common vole. Woody ESE, such as hedgerows, forest patches and strips, as well as rural built-up structures, attract generalist predators and enhance edge effects. ESE can be used as an effective management measure to curb and reduce outbreak hazards in farmland. Vole outbreak hazard predictions in Europe can be strengthened by integrating ESE spatial configuration derived from high-resolution remote sensing data (e.g. LiDAR) with long-term (> 6 years) and multi-scale monitoring of vole population dynamics.

Sea level cycles influenced land bridge formation and island connectivity throughout the Pleistocene, including the Sunda Shelf in SE Asia. Shelf-wide paleogeographic models are often based on few local observations and assumptions of tectonic uniformity. This study, using the Sunda Shelf as innovative example, compiles all published local vertical motion (VM) rates, assigns a reproducible reliability index – that accounts for methodological rigor, temporal precision, spatial accuracy, and source credibility – to each individual datapoint, and produces a harmonized VM raster. Our database synthesizes 93 VM datapoints, from 13 published sources of petrochemical exploration wells, fossil coral reef analysis, and seismostratigraphic proxies of varying spatial and temporal scales. Major tectonic boundaries, sedimentary basins, and structural zones were incorporated as barriers, while support points were added to steer interpolation in data poor areas. The created VM raster is a ready-to-use input for paleogeographic relative sea-level models, such as tabs (De Groeve et al., 2025). This study highlights the possibility and importance of a harmonized VM workflow to allow for intercomparison of paleogeographic studies and unlock the continental coastlines of Earth’s past.

Water table management such as temporal flooding is an important strategy for influencing vegetation development and creating suitable habitat for wildlife in managed wetland systems. Water table fluctuations can also affect soil carbon and nutrient cycling through changes in abiotic soil properties, plant traits and soil microbial communities, but research on the effect of temporal flooding on these relations is limited. Here we tested the hypothesis that winter inundation leads to a plant community with more fast-growth-related plant traits, a bacterial-dominated soil microbial community, and lower soil organic carbon stocks compared to a year-round dry grassland. We compared soil and vegetation of winter-inundated and non-inundated grassland in a Dutch-managed wetland area. In contrast to our hypothesis, we found that winter inundation results in plant communities with more slow-growth-related traits and microbial communities more dominated by fungi, compared to non-inundated grassland. We found no difference between shallow soil organic carbon stocks, carbon-to-nitrogen ratios or nitrogen-to-phosphorous ratios. Winter inundation did, however, change the relationship between soil and vegetation properties and soil carbon stocks, as well as soil nutrient ratios. While soil carbon stocks in non-inundated grassland were explained by abiotic soil and vegetation properties, soil carbon stocks were only explained by microbial properties in winter-inundated grasslands. These findings show that winter inundation can be used for vegetation and wildlife management with limited effects on soil carbon stocks.

This study extends the Sea-Level Sensitive dynamic model of marine island biogeography by integrating the dynamics of fusion-fission islands during glacial-interglacial cycles with marine island biogeography theory. We discuss the variations in littoral area due to Pleistocene sea-level changes and their effect on the evolutionary rates of splitting, extinction, and merging of populations, as well as on the speciation rates of marine shallow-water organisms. Here, we introduce three different types of fusion-fission islands: Solum islands, i.e., islands that have never been merged with neighbouring islands (at depths shallower than 50 m) during sea-level low stands associated with glacial episodes; Soror islands, i.e., islands that are subjected to fusion-fission cycles due to sea-level changes and thus may be functionally connected or separated depending on the amplitude of sea level changes; and Moliones islands, where two or more islands are functionally connected from a marine point of view, as the seafloor depth separating them is always shallower than 50 m, regardless of sea level. For this study, we selected 324 islands located in temperate and tropical climates, and representative of a broad geographic distribution, which were classified accordingly: 50 Solum islands, 77 islands making up 20 groups of Soror islands, and 197 islands from 34 groups of Moliones islands. Sea-level variation during glacial-interglacial cycles induced changes in the insular littoral area (ILA), resulting in five general types of curves of ILA change herein described. These ILA curves depend on the depth distribution across the shelves, which, in turn, depends on several variables, including the age of the island, the tectonic setting, the presence of submarine and subaerial terraces, and also on the presence/absence of coral reefs. Finally, we provide several predictions on the frequencies of marine population splitting, extinction, and merging events, as well as on the speciation rates of shallow-water marine organisms, according to the respective island types. Highlights We extend the Sea-Level Sensitive dynamic model of marine island biogeography theory to include the special case of fusion-fission islands. The dynamics of fusion-fission islands during glacial-interglacial cycles are relevant to evolutionary and biogeographic studies. We introduce new concepts (Solum, Soror, and Moliones islands) to designate islands according to the impact of glacial episodes and associated sea-level low stands on their marine biota. Five general types of curves of insular littoral area (ILA) change generated by sea-level variations during glacial-interglacial cycles are described. We hypothesize that the frequencies of marine population splitting, extinction, and merging events, as well as the speciation rates of shallow-water marine organisms, vary according to the island type.

Past climate fluctuations have profoundly influenced the global distribution of biomes, ecosystems and species, altering their altitude, spatial configuration, area, and connectivity. Notable examples include island archipelagos and alpine biomes, where shifts in sea levels and forest lines respectively reshaped their spatial structures. To understand how such changes affected species distributions and biodiversity patterns, we require spatially explicit reconstructions over continuous time series. However, a comprehensive and reproducible methodology that captures their spatio-temporal dynamism is lacking. Here, we introduce the R package Temporal Altitudinal Biogeographic Shifts (tabs), a tool designed for reconstructing spatial configurations over time, focusing on biogeographic systems bounded by an altitudinal range. We demonstrate the use of tabs by modelling spatial configurations of island archipelagos and alpine biomes in response to fluctuations in sea levels and forest lines. Unique to tabs, it can also account for geophysical effects on regional sea levels, and for geotectonic topographic changes. Beyond past reconstructions, tabs can project spatial configurations shaped by future climatic conditions. This versatile package is easily adaptable to various altitude-bounded biogeographic systems influenced by long-term climatic variations, such as coral reefs and shelf seas. Studying the shifts in biogeographic systems through continuous spatial reconstructions, rather than snapshots in time such as the Last Glacial Maximum, captures the nuances of continuously changing environments and provides a more complete understanding of the biogeography of our planet. tabs R package enables detailed spatio-temporal reconstructions of biogeographic systems along altitudinal gradients. Designed with user-friendliness in mind, it offers a streamlined setup, enabling researchers to start reconstructions quickly without extensive technical expertise. tabs is applicable to diverse biogeographic systems, including islands, coastal zones, and alpine biomes. It provides flexibility to tailor input data, parameters, and settings according to specific local conditions and research objectives. tabs generates outputs using a standardised data structure and open data formats, enabling effective analysis and presentation of results.

Since the Last Glacial Maximum (LGM) ~21.5 kya, global sea-level rise has reshaped islands by contracting areas, fragmentation, and severing mainland connections. These changes led to supersaturation of island communities, triggering community relaxation through local extinctions. However, whether local extinctions occur randomly or deterministically remains unclear. Here, we integrate a paleo-coastline model with well-characterised squamate community data from 163 Mediterranean islands to assess how past geographical changes influenced community structure. We evaluate phylogenetic and functional community structure and test links to paleogeographic variables using multivariate regressions. Our findings suggest overdispersion dominates and is higher on older islands, implying ongoing community relaxation and that extinctions are driven more by interspecific competition than environmental filtering. Island time-since-isolation emerges as the strongest predictor of phylogenetic diversity, indicating that longer isolation drives higher phylogenetic diversity via selective extinction of close relatives. These results underline the significance of relaxation dynamics in shaping insular communities.

Paleoclimatic variations have profoundly influenced the global distribution of ecosystems and habitats, altering their altitude, spatial configuration, area, and connectivity. Notable examples include island archipelagos and alpine biomes, where shifts in sea-levels and forest lines respectively reshaped their spatial structures. To understand how such changes affected species distributions and biodiversity patterns, we require spatially-explicit reconstructions over continuous time series. However, a comprehensive and reproducible methodology that captures their spatio-temporal dynamism is lacking. Here, we introduce the R package Temporal Altitudinal Biogeographic Shifts (TABS), a tool designed for reconstructing spatial configurations over time, focusing on biogeographic systems bounded by an altitudinal range. We demonstrate the use of TABS by modelling spatial configurations (‘shapes’) of island archipelagos and alpine biomes in response to modulations in sea-levels and forest lines. Unique to TABS, it can also account for crustal deformation due to ice sheet loading and gravitational forces, and for geotectonic and geophysical topographic changes. Beyond past reconstructions, TABS can project spatial configurations shaped by future climatic conditions. This versatile package is easily adaptable to various altitude-bounded biogeographic systems influenced by long-term climatic variations, such as coral reefs and sea shelves. Studying the shifts in biogeographic systems through continuous spatial reconstructions, rather than snapshots in time such as the Last Glacial Maximum, captures the nuances of continuously changing environments and provides a more complete understanding of the biogeography of our planet.

Outbreaks of the common vole, Microtis arvalis (Pallas, 1778), have plagued temperate European farmlands throughout history, causing large-scale crop loss and forming reservoirs for zoonotic pathogens. Here, we review the role of landscape heterogenicity, in particular ecological structural elements (ESEs) such as hedgerows, flower strips and bushes in farmlands on the outbreak dynamics of the common vole. Research into the role of landscape heterogeneity on outbreak dynamics in agricultural landscapes has highlighted the potential significance of the scale and connectivity of vole habitats, as well as various ecological structural elements that indirectly shape competition and predation. Landscape openness, in the form of open grasslands, such as crops and pastures, forms optimal vole habitat and has been linked to multiannual cycling and outbreaks of common vole populations. Conversely, ESEs that provide heterogeneity in agricultural landscapes are found to exert a limiting force on population growth and the likelihood of outbreaks. A heterogenic landscape not only creates physical barriers between vole populations, but also offers habitat and hunting arenas for both generalist and specialist predators. Especially woody ESEs, such as hedgerows, forest patches and strips, as well as rural built-up structures, stand out as features relevant for generalist predators. In addition, we find that rotary shallow tilling of fields is also effective in avoiding the establishment of vole populations. We find that there is evidence to support recommendations for effective landscape structure in farmland regions at three spatial scales: patch (2), landscape (< 100 km²) and regional (>100 km²). However, to further our understanding of the interaction between voles and landscape heterogeneity, it is essential to increase long-term (>6 years) and multi-scale monitoring projects of vole dynamics across all scales. Based on our review, we provide concrete management measures to exploit ELEs to reduce outbreak hazards in farmland. We conclude that there is now potential to identify outbreak hazards within farmlands on all three scales by large-scale high-resolution mapping of the geographic configuration of ELEs, using open-access high-resolution (< 1 m²) remote sensing data (LiDAR).