Gerold Kier

A global assessment of endemism and species richness across island and mainland regions

Endemism and species richness are highly relevant to the global prioritization of conservation efforts in which oceanic islands have remained relatively neglected. When compared to mainland areas, oceanic islands in general are known for their high percentage of endemic species but only moderate levels of species richness, prompting the question of their relative conservation value. Here we quantify geographic patterns of endemism-scaled richness (“endemism richness”) of vascular plants across 90 terrestrial biogeographic regions, including islands, worldwide and evaluate their congruence with terrestrial vertebrates. Endemism richness of plants and vertebrates is strongly related, and values on islands exceed those of mainland regions by a factor of 9.5 and 8.1 for plants and vertebrates, respectively. Comparisons of different measures of past and future human impact and land cover change further reveal marked differences between mainland and island regions. While island and mainland regions suffered equally from past habitat loss, we find the human impact index, a measure of current threat, to be significantly higher on islands. Projected land-cover changes for the year 2100 indicate that land-use-driven changes on islands might strongly increase in the future. Given their conservation risks, smaller land areas, and high levels of endemism richness, islands may offer particularly high returns for species conservation efforts and therefore warrant a high priority in global biodiversity conservation in this century.

Measuring and mapping endemism and species richness: a new methodological approach and its application on the flora of Africa

The adjustment of an existing index which combines endemism and species richness (Williams 1993) is proposed so that it requires markedly less data on the study area and its flora or fauna than was necessary with the conventional calculation method. Using this adjusted method, the resulting scores are calculated and mapped for the seed plant flora of the 20 African regions as delineated by White (1983). We argue that this index, here referred to as a measure of ‘endemism richness’, can be regarded as the specific contribution of an area to global biodiversity. We demonstrate that at a given sampling scale it shows a linear relation with area. We further demonstrate that, within certain limits, this linearity can also be observed in many cases when sampling scales vary which makes the comparison of differently sized geographic units easier than is the case for species richness. The two most important advantages over species richness are that this index is more suitable to measure both the conservation value of an area and the negative impact of invaders. The latter quality is due to the fact that it yields scores which usually do not rise substantially but can rather be expected to drop in many cases when an area is invaded by alien species.

Projected impacts of climate change on regional capacities for global plant species richness

Climate change represents a major challenge to the maintenance of global biodiversity. To date, the direction and magnitude of net changes in the global distribution of plant diversity remain elusive. We use the empirical multi-variate relationships between contemporary water-energy dynamics and other non-climatic predictor variables to model the regional capacity for plant species richness (CSR) and its projected future changes. We find that across all analysed Intergovernmental Panel on Climate Change emission scenarios, relative changes in CSR increase with increased projected temperature rise. Between now and 2100, global average CSR is projected to remain similar to today (+0.3%) under the optimistic B1/+1.8°C scenario, but to decrease significantly (−9.4%) under the ‘business as usual’ A1FI/+4.0°C scenario. Across all modelled scenarios, the magnitude and direction of CSR change are geographically highly non-uniform. While in most temperate and arctic regions, a CSR increase is expected, the projections indicate a strong decline in most tropical and subtropical regions. Countries least responsible for past and present greenhouse gas emissions are likely to incur disproportionately large future losses in CSR, whereas industrialized countries have projected moderate increases. Independent of direction, we infer that all changes in regional CSR will probably induce on-site species turnover and thereby be a threat to native floras.

Vascular Plant Diversity in a Changing World: Global Centres and Biome-Specific Patterns

We summarize research on the global centres and gradients of vascular plant diversity. Most centres of plant species richness are located in geodiverse areas of the humid tropics and sub-tropics, especially in forest biomes. When focussing on the rarity of the flora, islands play an outstanding role. Endemism-scaled richness of oceanic island floras (endemism richness) exceeds those of mainland regions by several-fold. In contrast to the situation for most other groups of organisms, biodiversity patterns are relatively well understood for plants and vertebrates. However, plant diversity of some of the most important centres is still insufficiently documented – an important impediment for its conservation and sustainable use. Though habitat conversion and overexploitation have yet the most severe impact on plant diversity, future climate change is adding an additional threat. This will likely affect plant diversity, especially in low-latitude countries, which contributed least to the human-induced greenhouse gas emissions.

Biologische Vielfalt zwischen Wandel und Veränderung

Der Mensch ist in hohem Mase von der Vielfah an Pflanzen, Tieren und Mikroorganismen auf der Erde abhangig. Diese biologische Vielfah, auch als Biodiversitat bezeichnet, wird auf dem weltweiten Masstab durch menschliche Aktivitaten erheblich reduziert. Einer Erforschung der gesamten Diversitat stehen immer noch gravierende Wissensdefizite im Wege, so dass hierfur auf Indikatorgruppen zuruckgegriffen werden muss. Die Gefaspflanzen eignen sich fur diese Funktion in besonderem Mase, da sie in terrestrischen Lebensraumen eine zentrale okologische Rolle spielen, vergleichsweise gut erforscht sind und von groser okonomischer, in vielerlei Hinsicht sogar von existentieller Bedeutung fur den Menschen sind. Die biologische Vielfalt weist, gemessen am Artenreichtum der Gefaspflanzen, in den feuchten Tropen und Subtropen die hochsten Werte auf Insbesondere in den Gebirgsregionen ist die Biodiversitat auf dem Masstab von 10.000 km2 besonders hoch, was mit der hohen Geodiversitat dieser Gebiete, d.h. ihrer Vielfah an abiotischen Faktoren, erklart werden kann. In diesem Zusammenhang muss jedoch betont werden, dass Biodiversitat sowohl vom Betrachtungsmasstab als auch vom zugrundeliegenden Qualitatskriterium abhangig ist. Die Artenzahl ist hierbei nur eines — wenn auch aus guten Grunden das meistverwendete — von vielen Kriterien. Ein weiteres Kriterium ist z.B. der Anteil von durch den Menschen eingeschleppten Arten, die oftmals eine Bedrohung fur die einheimische Biodiversitat darstellen. Um den Erhah der biologischen Vielfah zu sichern, ist eine Reihe von Masnahmen erforderlich. Neben dem Schutz in naturlichen Lebensraumen bietet auch der ex-situSchutz, z.B. in Botanischen Garten, in Teilbereichen Chancen fur eine Bewahrung unseres naturlichen Erbes.

Biodiversität — Globale Dimension und Verteilung genetischer Vielfalt

Noch vor 20 Jahren war die Fachwelt uberzeugt, das die Artenvielfalt unseres Planeten in Grundzugen bekannt sei. Seit Carl von Linne vor 250 Jahren sein „Systema Naturae“ erarbeitete, hatten Naturforscher schlieslich systematisch die Lebewesen in unserer Umwelt beschrieben und klassifiziert. Bis heute sind rund 1,7 Millionen Tier-, Pflanzen- und Mikroorganismenarten wissenschaftlich erfast. Schon Anfang der achtziger Jahre zeigten aber Forschungen v.a. im Kronendach tropischer Regenwalder, das der weitaus groste Teil der auf unserer Erde lebenden Arten noch unentdeckt ist.