World's Terrestrial Ecosystems Research Articles

A Decision-Support Tool to Augment Global Mountain Protection and Conservation, including a Case Study from Western Himalaya

Mountains are remarkable storehouses of global biodiversity that provide a broad range of ecosystem services underpinning billions of livelihoods. The world’s network of protected areas includes many iconic mountain landscapes. However, only ca. 19% of mountain areas globally are protected (excluding Antarctica); many mountain areas are inadequately (<30% of their total terrestrial area) or completely unprotected. To support the UN Convention on Biological Diversity’s Global Biodiversity Framework goal of protecting at least 30% of the world’s lands by 2030, we have developed a strategic decision-support tool for identifying and prioritizing which candidate mountain areas most urgently require protection. To test its efficacy, we applied the tool to the Western Himalaya Case Study Area (WHCSA). The six-step algorithm harnesses multiple datasets including mountain Key Biodiversity Areas (KBAs), World Terrestrial Ecosystems, Biodiversity Hotspots, and Red List species and ecosystems. It also makes use of other key attributes including opportunities for disaster risk reduction, climate change adaptation, developing mountain tourism, maintaining elevational gradients and natural ecological corridors, and conserving flagship species. This method resulted in nine categories of potential action—four categories for follow-up action (ranked by order of importance and priority), and five categories requiring no further immediate action (either because countries are inadequately equipped to respond to protection deficits or because their KBAs are deemed adequately protected). An area-based analysis of the WHCSA identified 33 mountain KBAs regarded as inadequately protected, which included 29 inadequately protected World Mountain Ecosystems. All 33 inadequately protected KBAs in the WHCSA are Category A1: first-priority mountain KBAs (located in the Himalaya Biodiversity Hotspot in developing countries), requiring the most urgent attention for protection and conservation. Priorities for action can be fine-filtered by regional teams with sufficient local knowledge and country-specific values to finalize lists of priority mountain areas for protection. This rapid assessment tool ensures a repeatable, unbiased, and scientifically credible method for allocating resources and priorities to safeguard the world’s most biodiverse mountain areas facing myriad threats in the Anthropocene.

Fire disturbance promotes biodiversity of plants, lichens and birds in the Siberian subarctic tundra.

Fire shapes the world's terrestrial ecosystems and has been influencing biodiversity patterns for millennia. Anthropogenic drivers alter fire regimes. Wildfires can amplify changes in the structure, biodiversity and functioning of the fast-warming tundra ecosystem. However, there is little evidence available, how these fires affect species diversity and community composition of tundra ecosystems over the long term. We studied long-term fire effects on community composition and diversity at different trophic levels of the food web in the subarctic tundra of Western Siberia. In a space-for-time approach we compared three large fire scars (>44, 28 and 12years old) to unburnt controls. We found that diversity (measured as species richness, Shannon index and evenness) of vascular and non-vascular plants and birds was strongly affected by fire, with the greatest species richness of plants and birds for the intermediate-age fire scar (28years). Species composition of plants and birds still differed from that of the control >44years after fire. Increased deciduous shrub cover was related to species richness of all plants in a hump-shaped manner. The proportion of southern (taiga) bird species was highest in the oldest fire scar, which had the highest shrub cover. We conclude that tundra fires have long-term legacies with regard to species diversity and community composition. They may also increase landscape-scale species richness and facilitate range expansions of more southerly distributed species to the subarctic tundra ecosystem.

Suitable Days for Plant Growth Disappear under Projected Climate Change: Potential Human and Biotic Vulnerability.

Ongoing climate change can alter conditions for plant growth, in turn affecting ecological and social systems. While there have been considerable advances in understanding the physical aspects of climate change, comprehensive analyses integrating climate, biological, and social sciences are less common. Here we use climate projections under alternative mitigation scenarios to show how changes in environmental variables that limit plant growth could impact ecosystems and people. We show that although the global mean number of days above freezing will increase by up to 7% by 2100 under “business as usual” (representative concentration pathway [RCP] 8.5), suitable growing days will actually decrease globally by up to 11% when other climatic variables that limit plant growth are considered (i.e., temperature, water availability, and solar radiation). Areas in Russia, China, and Canada are projected to gain suitable plant growing days, but the rest of the world will experience losses. Notably, tropical areas could lose up to 200 suitable plant growing days per year. These changes will impact most of the world’s terrestrial ecosystems, potentially triggering climate feedbacks. Human populations will also be affected, with up to ~2,100 million of the poorest people in the world (~30% of the world’s population) highly vulnerable to changes in the supply of plant-related goods and services. These impacts will be spatially variable, indicating regions where adaptations will be necessary. Changes in suitable plant growing days are projected to be less severe under strong and moderate mitigation scenarios (i.e., RCP 2.6 and RCP 4.5), underscoring the importance of reducing emissions to avoid such disproportionate impacts on ecosystems and people.

Past Ecosystem Dynamics in Fashioning Views on Conserving Extant New World Vegetation1

In the Cretaceous there were eight New World terrestrial ecosystems that were distinct or only shadowy versions of those present today. Now, 65 Ma later, 12 ecosystems constitute the recognizable subdivisions of the Earth's living and physical envelope. Knowledge of the intervening history is useful for conservation in several regards. It reveals how heterogeneous modern systems are in age and origin (e.g., lowland Neotropical rainforest formed between ca. 60 and 58 Ma; tundra and páramo between ca. 5 and 3 Ma), how individualized the response of component species to previous environmental change has been, and how levels of biodiversity have fluctuated through time. History provides approximate analogs for conditions anticipated in the near future and estimates of the biotic response. In addition, history documents that climatic events originally discovered and formerly associated with the high latitudes also affected tropical regions, and that discovery constitutes a valuable context for assessing previously held views about the stability of tropical communities and environments. There has been a rapid increase in the pace of both natural and human-induced environmental change and biotic response approaching modern times. Blurring the lines between neontology and paleontology, namely, conceptualizing ecosystems over Cretaceous and especially Late Cenozoic time, provides a dynamic view of these systems and furthers realistic strategies to conserve them.

Sequencing New World Ecosystems: Comparison of the Cretaceous and Cenozoic Appearance of Habitats with Biome-Characterizing Plant Groups1

Concepts about development of the plant component of New World terrestrial ecosystems through deep time have reached a point where it is possible to consider some subtle and refining details about the process. One such detail is the temporal relationship between the opportunity of new habitats provided by the physical processes of landscape development and long-term climate change, and the availability of the mostly angiosperm lineages that presently occupy these habitats. Some habitats (e.g., beach/strand/dune) were in existence long before the rise of the flowering plants ca. 125 million years ago (Ma), and some did not develop until late in the Neogene from a combination of cooling climates and locally to regionally increasing elevations (alpine tundra/páramo). In other instances, both habitats and lineages existed contemporaneously, but in different parts of the world, so development of the particular ecosystem had to await the appearance and spread in the New World of the lineage through migration (e.g., Rhizophora L. into modern mangrove habitats after the Late Eocene; Quercus L. from the north into modern oak–Weinmannia L. habitats only after 330 thousand years ago (Kyr). The temporal correspondence between opportunity and availability joins the more widely recognized forcing mechanisms of geologic and climate change, acting on evolutionary processes, as one additional factor in better understanding the origin, composition, and distribution of the ecosystems that presently characterize the New World.

Photosynthesis in Balance with Respiration?

Photosynthesis in Balance with Respiration?

Why are estimates of the terrestrial carbon balance so different?

AbstractThe carbon balance of the world's terrestrial ecosystems is uncertain. Both top‐down (atmospheric) and bottom‐up (forest inventory and land‐use change) approaches have been used to calculate the sign and magnitude of a net terrestrial flux. Different methods often include different processes, however, and comparisons can be misleading. Differences are not necessarily the result of uncertainties or errors, but often result from incomplete accounting inherent in some of the methods. Recent estimates are reviewed here. Overall, a northern mid‐latitude carbon sink of approximately 2 Pg C yr−1 appears robust, although the mechanisms responsible are uncertain. Several lines of evidence point to environmentally enhanced rates of carbon accumulation. Other lines suggest that recovery from past disturbances is largely responsible for the sink. The tropics appear to be a small net source of carbon or nearly neutral, and the same uncertainties of mechanism exist. In addition, studies in the tropics do not permit an unequivocal choice between two alternatives: large emissions of carbon from deforestation offset by large sinks in undisturbed forests, or moderate emissions from land‐use change with essentially no change in the carbon balance in undisturbed forests. Resolution of these uncertainties is most likely to result from spatially detailed historical reconstructions of land‐use change and disturbance in selected northern mid‐latitude regions where such data are available, and from systematic monitoring of changes in the area of tropical forests with satellite data of high spatial resolution collected over the last decades and into the future.

Ecology of Soil Erosion in Ecosystems

Each year, about 75 billion tons of soil are eroded from the world's terrestrial ecosystems. Most agricultural land in the world is losing soil at rates ranging from 13 tons/ha/year to 40 tons/ha/year. Because soil is formed very slowly, this means that soil is being lost 13–40 times faster than the rate of renewal and sustainability. Rain and wind energy are the two prime causes of erosion from tilled or bare land. Erosion occurs when the soil lacks protective vegetative cover. Soil erosion reduces the productivity of the land by loss of water, soil organic matter, nutrients, biota, and depth of soil. The greatest threat to providing food for a rapidly growing human population is soil erosion. Abandoned, eroded agricultural land is replaced by clearing forested ecosystems.

Equilibrium analysis of carbon pools and fluxes of forest biomes in the former Soviet Union

Natural processes in ocean and terrestrial ecosystems together with human activities have caused a measurable increase in the atmospheric concentration of CO2. It is predicted that an increase in the concentration of CO2 will cause the Earth's temperatures to rise and will accelerate rates of plant respiration and the decay of organic matter, disrupting the equilibrium of the terrestrial carbon cycle. Forests are an important component of the biosphere, and sequestration of carbon in boreal forests may represent one of the few realistic alternatives to ameliorate changes in atmospheric chemistry. The former Soviet Union has the greatest expanse of boreal forests in the world; however, the role of Soviet forests in the terrestrial carbon cycle is not fully understood because the carbon budget of the Soviet forest sector has not been established. In recognition of the need to determine the role of Soviet forests in the global carbon cycle, the carbon budget of forest biomes in the former Soviet Union was assessed based on an equilibrium analysis of carbon cycle pools and fluxes. Net primary productivity was used to identify the rate of carbon turnover in the forest biomes. Net primary productivity was estimated at 4360 Mt of carbon, the vegetation carbon pool was estimated at 110 255 Mt, the litter carbon pool was estimated at 17 525 Mt, and the soil carbon pool was estimated at 319 100 Mt. Net primary productivity of Soviet forest biomes exceeded industrial CO2 emissions in the former Soviet Union by a factor of four and represented approximately 7% of the global terrestrial carbon turnover. Carbon stores in the phytomass and soils of forest biomes of the former Soviet Union represented 16% of the carbon concentrated in the biomass and soils of the world's terrestrial ecosystems. All carbon pools of Soviet forest biomes represented approximately one-seventh of the world's terrestrial carbon pool.

Modeling Terrestrial Ecosystems in the Global Carbon Cycle With Shifts in Carbon Storage Capacity by Land‐Use Change

A five—compartment model for carbon cycling in the world's terrestrial ecosystems, which includes a concise treatment of the releases of carbon and shifts in carbon storage due to forest clearing, is presented. The dynamics of the less abundant isotopes, 13C and 14C, are included in the model to allow interpretation of available isotopic time series. The sensitivity of the net carbon flux between the terrestrial component of the model and the atmosphere to 10% variability in terrestrial rate coefficients and grown parameters is examined; for the particular case considered here, the variability in model response is °10%. Response of the model agrees reasonably well with observations of historical changes in the specific activity of 14C in the atmosphere. The model—calculated Seuss effect in 1952 is 2%, and the time constant of the expotential decrease in atmospheric 14C following the weapons test ban is 14 yr. By adjusting the releases of carbon due to forest clearing, a fit of model response to 13C/12C tree—ring time series is derived. The resulting forest—clearing carbon release function rises to 2.5 Pg/yr by 1910 and remains constant to the present. Due to establishment of ground vegetation following clearing, the net carbon flux from the terrestrial biotic system to the atmosphere is less than the release due to clearing in some instances. To accommodate this net input to the atmosphere in addition to that due to fossil fuel combustion, the pre—industrial CO2 concentration must be assumed to have been lower than is implied by extrapolating the modern instrument records backward in time.

Why Are There So Many Kinds of Flowering Plants?

The world is amazingly rich in the numbers of living species of plants and animals; understanding this diversity and explaining its origin continues to be a central issue in evolutionary biology. Whether working in the dry, but speciesrich, Sonoran Desert or in the epiphyteladen cloud forests in Central America, one is confronted by the same general question: What factors have caused such diverse communities to evolve? In a stimulating paper on animal diversity, Hutchinson (1959) pointed out that the species richness of the contemporary biota on land far exceeds species numbers in the oceans. He suggested that flowering plants have played a major role in the evolution of terrestrial diversity. There is no compelling evidence for the existence of angiosperms before the Cretaceous, but recently scientists have acquired a much more detailed understanding of their differentiation in the Middle Cretaceous (Dilcher 1979, Doyle 1977, Doyle and Hickey 1976). Since then, the flowering plants have come to dominate a great majority of the world's terrestrial ecosystems.