Plant Extinction Research Articles

The human exposome and health in the Anthropocene.

‘Man is a part of nature, and his war against nature is inevitably a war against himself’ ― Rachel Carson. The term Anthropocene describes the current period, when the biophysical systems of Earth are being significantly altered by human activities. Although the great acceleration of anthropogenic influences began in the 20th century, the Industrial Revolution has often been proposed as the start of this period. Burning fossil fuels on a large scale, which was the motor of the Industrial Revolution, has disrupted the global climate, with far-reaching consequences for life on Earth. In the Intergovernmental Panel on Climate Change (IPCC) Special Report, it is stated with high confidence that human activities have significantly contributed to an increase in the global mean temperature of approximately 1°C above pre-industrial levels, and with medium confidence that trends in intensity and frequency of some climate and weather extremes have been detected, during which approximately 0.5°C of global warming occurred.1 The average global temperature will continue to rise if current greenhouse gas emissions continue. The Copernicus Climate Change Service (C3S) recently reported that the 5 warmest years on record have all occurred in the past 5 years, and that 2010–19 was the warmest decade recorded. C3S also reported that 2019 was globally the second warmest year and that atmospheric carbon dioxide (CO2) concentrations continued to rise.2 During 2019 there was extraordinary ice-melt in Greenland and wildfires consumed millions of acres in Siberia, Alaska and Australia.3,4 Brazil’s national institute for space research (INPE) also reported fires burning at a record rate in the Amazon rainforest. The INPE reported an 80% increase in deforestation compared with that in the same period in 2018. This not only threatens local ecosystems but may affect the entire planet, because intact forest absorbs and holds large amounts of CO2.5 The recent Living Planet Report by the World Wildlife Fund and Zoological Society of London provides further evidence that unsustainable human activity is threatening the planet’s natural systems.6 The report shows an overall decline of 60% in species’ population sizes between 1970 and 2014 because of factors such as overexploitation, habitat destruction (e.g. agricultural land expansion and logging), environmental pollution and climate change. The current species extinction rates are between 100 and 1000 times higher than previous background rate.6 The International Union for Conservation of Nature Red List 2019 reported that more than 27 000 species are threatened with extinction (27% of all animal, fungi and plant species assessed).7 A recent study of plants that have become extinct since Carl Linnaeus’ Species Plantarum has concluded that the number of known seed plant extinctions is more than four times that of the Red List.8 Biodiversity is a vital part of Earth’s past, present and future, and a key indicator of planetary health. The ongoing dramatic decline in biodiversity is therefore a problem, and underlying causes must be better understood for effective species conservation and human well-being. The concept of planetary health focuses on the intricate link between human health and the health of natural systems within the biosphere.9–11 Loss of biological diversity alters ecosystems functions and thereby reduces the ability to provide society with the goods and services, including food, necessary to flourish.9–11 The emergence of viruses such as the novel coronavirus (SARS-CoV-2), and global environmental change, wildlife, animal markets and food systems (which contribute largely to carbon emissions) are also interrelated.12,13 To increase awareness of current environmental problems and how complex interactions among climate change, infectious agents, environmental pollutants and other stressors, i.e. the exposome, may affect human health, this multidisciplinary review summarizes important scientific literature and discusses actions for a successful transformation to a safe, sustainable society.

To clean or not to clean: Cleaning open‐source data improves extinction risk assessments for threatened plant species

AbstractPlants are under‐represented in conservation efforts, with only 9% of described species published on the IUCN Red List. Biodiversity aggregators including the Global Biodiversity Information Facility (GBIF) and the more recent Botanical Information and Ecology Network (BIEN) contain a wealth of potentially useful occurrence data. We investigate the influence of these data in accelerating plant extinction risk assessments for 225 endemic, near‐endemic, and socioeconomic Bolivian plant species. Geo‐referenced herbarium voucher specimens verified by taxonomic experts comprised our control data set. Open‐source data for 77 species was subjected to a two‐stage cleaning protocol (using an automated R package followed by a manual clean) and threat categories were computed based on extent of occurrence thresholds. Accuracy was the highest using cleaned GBIF data (76%) and uncleaned BIEN data (79%). Sensitivity was the highest for cleaned GBIF (73%) and BIEN (80%) data suggesting our cleaning protocol was essential to maximize sensitivity rates. Comparisons between the control, GBIF and BIEN data sets revealed a paucity of occurrence data for 148 species (66%), 72% of which qualified for a threatened category. Balancing data quantity and accuracy must be considered when using open‐source data. Filling data gaps for threatened species is a conservation priority to improve the coverage of threatened species within biodiversity aggregators.

Determinants of Tubastraea coccinea invasion and likelihood of further expansion in the northern Gulf of Mexico

Invasive species have large economic and ecological impacts and are the leading driver of extinction for both plants and animals worldwide. In the USA, coral reefs, which provide $3.4 billion per year in ecosystem services, are impacted by invasive marine species. One such species is Tubastraea coccinea, which was the first scleractinia to invade the western Atlantic and recently has spread to natural reefs within the northern Gulf of Mexico (GoM). We document this recent invasion by compiling occurrence records, develop a species distribution model identifying important determinants of invasion, and project potential range expansion. Our results indicate T. coccinea currently is distributed along the GoM coast from the Florida Keys to southern Texas, with documented localities clustered ≈ 100 km off the Louisiana coast and ≈ 200 km off the Texas coast, and sparsely distributed elsewhere. Our species distribution model identified five environmental factors that together contribute > 99% to the overall model. These factors include two surface variables (mean pH and mean calcite, contributing ≈ 40%) and three benthic variables (maximum current velocity, minimum iron, and minimum dissolved oxygen, contributing ≈ 60%). Our model suggests potential habitat for range expansion is distributed mainly within the western portion of the northern GoM, with the highest probabilities of occurrence (0.8 < P < 1.0) clustered along the Texas and Louisiana coasts between 88 and 97° W (near the border between states).

Robustness of a meta‐network to alternative habitat loss scenarios

Studying how habitat loss affects the tolerance of ecological networks to species extinction (i.e. their robustness) is key for our understanding of the influence of human activities on natural ecosystems. With networks typically occurring as local interaction networks interconnected in space (a meta‐network), we may ask how the loss of specific habitat fragments affects the overall robustness of the meta‐network. To address this question, for an empirical meta‐network of plants, herbivores and natural enemies we simulated the removal of habitat fragments in increasing and decreasing order of area, age and connectivity for plant extinction and the secondary extinction of herbivores, natural enemies and their interactions. Meta‐network robustness was characterized as the area under the curve of remnant species or interactions at the end of a fragment removal sequence. To pinpoint the effects of fragment area, age and connectivity, respectively, we compared the observed robustness for each removal scenario against that of a random sequence. The meta‐network was more robust to the loss of old (i.e. long‐fragmented), large, connected fragments than of young (i.e. recently fragmented), small, isolated fragments. Thus, young, small, isolated fragments may be particularly important to the conservation of species and interactions, while contrary to our expectations larger, more connected fragments contribute little to meta‐network robustness. Our findings highlight the importance of young, small, isolated fragments as sources of species and interactions unique to the regional level. These effects may largely result from an unpaid extinction debt, whereby younger fragments are likely to lose species over time. Yet, there may also be more long‐lasting effects from cultivated lands (e.g. water, fertilizers and restricted cattle grazing) and network complexity in small, isolated fragments. Such fragments may sustain important biological diversity in fragmented landscapes, but maintaining their conservation value may depend on adequate restoration strategies.

Effects of Elevated Temperature on the Tropical Soil Bacterial Diversity

Bacteria are important biological components of soil that play pivotal roles in improving soil quality and maintaining a balanced ecosystem. However, global climate change may have severe impacts on biodiversity and ecosystems including species loss and extinction of plants and animals, including microbes. Thus, it is crucial to determine how elevated temperature may alter soil bacterial diversity and composition. In this study, an in vitro simulated temperature rise experiment was carried out on soils from three sampling sites, referring to S1, S2, and S3 around Sabah, Malaysia. Soils were incubated at 25 °C (control) and 27 °C (simulated warming) with constant parameters in a growth chamber up to 16 months. Total DNA was extracted from microbes in the soil and used for PCR amplification targeting the V3-V4 region of the 16S rRNA gene. These amplicons were sequenced using the MiSeq platform (Illumina, USA). Raw DNA sequences were trimmed, merged, and aligned against the 16S rRNA sequences in the NCBI 16S database. The results showed that the analyzed soils were mainly dominated by Proteobacteria, Actinobacteria, Acidobacteria, and Verrucomicrobia. After 16 months of simulated warming, a net decrease of Proteobacteria, Acidobacteria, and Planctomycetes, and an increase of Actinobacteria and Chloroflexi were observed for all three soil samples, indicating that these phyla were highly affected by a temperature rise. At the genus level, Gaiella and Nocardioides exhibited a net increase while Bradyrhizobium, Mycobacterium, Tepidisphaera, and Paludibaculum demonstrated net decrease after 16 months of simulated warming. Knowledge on the changes of soil bacterial diversity patterns as a result of temperature elevation will contribute to select the best intervention strategy to overcome global warming issue in the future.

THE LAW OF INTERMITTENT EVOLUTION AND SELF-HEALING OF THE LIVING NATURE OF EARTH

The living nature of the Earth has an amazing property: its evolution is intermittent, it develops in separate stages, with the mass destruction of a large part of wildlife at the end of each stage, and with the subsequent selfhealing of almost all biodiversity for hundreds of thousands or millions of years. Self-healing was due to the presence of an information base - preserved wildlife. Several major natural mass extinctions of animals and plants are known, apparently related to volcanism, space influences, etc. After mass extinctions inevitably followed periods of biodiversity restoration. This development is in line with the author's concept of branching development. Therefore, the tree of evolution is multi-tiered, step-by-step. Extinctions served as natural filters, stopping the development of unpromising species, and supporting the emergence and development of promising species. But the coming period of man-made extinction is fundamentally different from the previous ones in that there used to be a base for biodiversity restoration - natural nature. For the first time, large man-made changes in the Earth's landscapes occurred in the last 150 - 200 years, during the scientific - technological revolution; they're in a good place ...in the components of landscapes ((e.g., the vital composition of air, water, extreme foresting, the limit of the development of nature, etc.).

The stratigraphy of latest Devonian and earliest Carboniferous rocks in Ireland

Thick successions of latest Devonian and early Carboniferous siliciclastic rocks of fluviatile and shallow marine origin are well exposed in numerous coastal sections in the south of Ireland. Correlations based on palynostratigraphy demonstrate that an overall northward transgression, in detail consisting of several fluctuations of relative sea level, resulted in the replacement of fluvial coastal plain environments by shallow marine conditions. The most conspicuous lithological record of transgression occurred at or close to the base of the Carboniferous, when a regionally distributed mudstone deposited in a shallow sea, replaced the generally sandy strata that had prevailed in the latest Devonian. There is no evidence for very large glacioeustatic changes of sea level related to the coeval western Gondwanan glaciation. Of the three horizons for a new GSSP for the base of the Carboniferous currently under review, the base of the Protognathodus kuehni Zone/basal Siphonodella sulcata Zone and coastal plant extinction is the most easily applied in Ireland and can be identified using palynology and corresponds to an easily recognised, extensively developed lithological change in the south of the country.

Vascular plant extinction in the continental United States and Canada.

Extinction rates are expected to increase during the Anthropocene. Current extinction rates of plants and many animals remain unknown. We quantified extinctions among the vascular flora of the continental United States and Canada since European settlement. We compiled data on apparently extinct species by querying plant conservation databases, searching the literature, and vetting the resulting list with botanical experts. Because taxonomic opinion varies widely, we developed an index of taxonomic uncertainty (ITU). The ITU ranges from A to F, with A indicating unanimous taxonomic recognition and F indicating taxonomic recognition by only a single author. The ITU allowed us to rigorously evaluate extinction rates. Our data suggest that 51 species and 14 infraspecific taxa, representing 33 families and 49 genera of vascular plants, have become extinct in our study area since European settlement. Seven of these taxa exist in cultivation but are extinct in the wild. Most extinctions occurred in the west, but this outcome may reflect the timing of botanical exploration relative to settlement. Sixty‐four percent of extinct plants were single‐site endemics, and many occurred outside recognized biodiversity hotspots. Given the paucity of plant surveys in many areas, particularly prior to European settlement, the actual extinction rate of vascular plants is undoubtedly much higher than indicated here.

Cretaceous–Paleogene plant extinction and recovery in Patagonia

AbstractThe Cretaceous–Paleogene (K/Pg) extinction appears to have been geographically heterogeneous for some organismal groups. Southern Hemisphere K/Pg palynological records have shown lower extinction and faster recovery than in the Northern Hemisphere, but no comparable, well-constrained Southern Hemisphere macrofloras spanning this interval had been available. Here, macrofloral turnover patterns are addressed for the first time in the Southern Hemisphere, using more than 3500 dicot leaves from the latest Cretaceous (Maastrichtian) and the earliest Paleocene (Danian) of Argentine Patagonia. A maximum ca. 90% macrofloral extinction and ca. 45% drop in rarefied species richness is estimated across the K/Pg, consistent with substantial species-level extinction and previously observed extirpation of host-specialized leaf mines. However, prior palynological and taxonomic studies indicate low turnover of higher taxa and persistence of general floral composition in the same sections. High species extinction, decreased species richness, and homogeneous Danian macrofloras across time and facies resemble patterns often observed in North America, but there are several notable differences. When compared with boundary-spanning macrofloras at similar absolute paleolatitudes (ca. 50°S or 50°N) from the Williston Basin (WB) in the Dakotas, both Maastrichtian and Danian Patagonian species richnesses are higher, extending a history of elevated South American diversity into the Maastrichtian. Despite high species turnover, our analyses also reveal continuity and expansion of leaf morphospace, including an increase in lobed and toothed species unlike the Danian WB. Thus, both Patagonian and WB K/Pg macrofloras support a significant extinction event, but they may also reflect geographically heterogeneous diversity, extinction, and recovery patterns warranting future study.

Modeled physiological mechanisms for observed changes in the late Paleozoic plant fossil record

Earth’s tropical forests repeatedly restructured on 105- to 107-year timescales during the Late Paleozoic Ice Age (340–280 Ma). Although it is established that these ancient plants responded to an evolving climate, their thresholds for physiological functioning and how such thresholds led to vegetation-climate feedbacks warrants further investigation. Here, we evaluate the physiology of seven plant types that dominated Middle Pennsylvanian through early Permian tropical lowland ecosystems. We apply taxa-specific leaf morphologic and geochemical measurements, time-specific atmospheric pCO2, pO2, and O2:CO2, and site-specific meteorology to Paleo-BGC, a modified version of the process-based ecosystem model Biome-BGC 4.2.1. Our study reveals four major findings. (1) The existence of pCO2 and precipitation thresholds for loss of physiological viability that provide a mechanism for replacement of wet-adapted lycopsids and medullosans by marattialean tree ferns, which were tolerant of periodic drought, and the subsequent dominance of seasonally dry-adapted cordaitaleans and conifers. These thresholds are relevant to both vegetation turnovers within glacial-interglacial cycles of the Pennsylvanian and to major restructuring events through the later Carboniferous and early Permian coincident with intensifying paleotropical aridification. (2) Under drier conditions, the combination of higher drought tolerance and primary productivity for marattialean tree ferns, conifers, and cordaitaleans provided an ecophysiological advantage over lycopsids and medullosans. (3) Our results further indicate that, although the shift to more drought-tolerant plants in the Late Pennsylvanian and early Permian could have led to increased biomass and surface runoff, their ability to affect climate was likely limited by aridity and changes in vegetation density. (4) Finally, our modeling shows that atmospheric pCO2 has a larger effect on physiological functioning than pO2. These findings highlight the unique insight into extinct plant function gained by coupling empirical measurements with ecosystem modeling and, in turn, the potential to physiologically constrain paleo-vegetation shifts previously inferred from the paleobotanical record.

A terrestrial Devonian-Carboniferous boundary section in East Greenland

Terrestrial Devonian-Carboniferous boundary sections are present in the East Greenland Devonian Basin. The boundary section on Stensiö Bjerg developed in deep, distal lake sediments with a pair of lakes representing the boundary. A diverse spore assemblage developed as the lake flooded the basin. Previously abundant spores, notably Retispora lepidophyta, Diducites spp., Rugospora radiata and all forms with bifurcate tips (Ancyrospora and Hystricosporites), then became extinct through just over a metre of section. The spore assemblage is then lost into AOM rich very high TOC% lake sediments. There is a negative δ13CTOC excursion in the Stensiö Bjerg section interpreted to represent the upper part of the positive excursion known from marine sections. The upper lake contains the simple VI spore assemblage of the earliest Carboniferous age. The correlative section on Rebild Bakker was developed in shallow proximal facies without AOM and shows that a Devonian-Carboniferous LN* to VI spore zone boundary can be picked in the lower lake based on the last occurrence of Retispora lepidophyta in an assemblage otherwise dominated by simple spores and Grandispora cornuta. Spores in this VI spore assemblage, particularly Grandispora cornuta, show sculpture malformation that is entirely characteristic of UV-B radiation damage to their DNA prior to deposition of its protective wall layer. This palynological record showing the rapid extinction of major elements within the Late Devonian microflora can be reconciled with accounts claiming there was no mass extinction of plants and spores across the boundary. The palaeobiology of the major spore groups that became extinct is reviewed.

English

The incidence of snake bite in rural West Africa is reportedly high with an 11&ndash;17% mortality rate. Nigeria has one third of the cases for snake bite cases in this region.Thus, most tribes in North-western part of Nigeria depend on medicinal plants for snakebites. However, it appears that a gap exists on documentation of these plants especially tropical flora used in the management of snake bite. This led to increase depletion of medicinal plant resources and knowledge of their traditional use. Consequently, this survey provided knowledge and data on medicinal plants use in management of snake bite which will help retard the current rate of extinction and decimation of the medicinal plants in these areas and then provide need to conserve what is left as medicinal plants for posterity sake. The study was carried in three northwestern states of Nigeria namely Sokoto, Kebbi and Zamfara for three months. A semi-structured questionnaire was administered and fourteen respondents made up of herb sellers (7%), traditional medical practitioners (93%). The majority of the respondents were male (100%) and 34% were above 50 years of age.&nbsp; From the study, the data collected shows 25 medicinal plants were in use by different categories of practitioners. Botanical names, local names, family names, plant part (s) use and number of citations were also obtained and documented. Key words: North-western Nigeria, snakebites, medicinal plants. &nbsp

Terrestrial ecosystem collapse and soil erosion before the end-Permian marine extinction: Organic geochemical evidence from marine and non-marine records

A terrestrial ecosystem collapse event accompanied by extensive soil erosion has been widely recorded in marine sedimentary rocks at the vicinity of the end-Permian mass extinction. However, the precise timing of this event and its impact on the marine extinction have not yet been ascertained. Here we present an organic geochemical study of non-marine and marine sections from the South China Craton, which shows that terrestrial ecosystem collapse was accompanied by a soil erosion event, and was followed by the end-Permian marine extinction. Two separate events devastated the terrestrial ecosystem prior to the marine extinction event, over a timespan of dozens of kyr. Bacteria flourished in the non-marine section coeval with a decline in terrestrial plants and in the marine section during the end-Permian marine extinction. A proto-recovery of herbaceous plants (not woody plants) occurred dozens of kyr after the end-Permian marine extinction and coincided with a global warming maximum and oceanic anoxia/euxinia. • Plant extinction was followed by soil erosion and the end-Permian marine extinction. • Bacteria flourished during the plant extinction in the non-marine section. • Bacteria flourished during the end-Permian marine extinction in the marine section. • Proto-recovery of vegetation coincided with global warming and oceanic euxinia.

Extinction risk and threats to plants and fungi

Societal Impact StatementThere is increasing awareness that plants and fungi, as natural solutions, can play an important role in tackling ongoing global environmental challenges. We illustrate how understanding current and projected threats to plants and fungi is necessary to manage and mitigate risks, while building awareness of gaps and bias in current assessment coverage is essential to adequately prioritize conservation efforts. We highlight the state of the art in conservation science and point to current methods of assessment and future studies needed to mitigate species extinction.SummaryPlant and fungal biodiversity underpin life on earth and merit careful stewardship in an increasingly uncertain environment. However, gaps and biases in documented extinction risks to plant and fungal species impede effective management. Formal extinction risk assessments help avoid extinctions, through engagement, financial, or legal mechanisms, but most plant and fungal species lack assessments. Available global assessments cover c. 30% of plant species (ThreatSearch). Red List coverage overrepresents woody perennials and useful plants, but underrepresents single‐country endemics. Fungal assessments overrepresent well‐known species and are too few to infer global status or trends. Proportions of assessed vascular plant species considered threatened vary between global assessment datasets: 37% (ThreatSearch), and 44% (International Union for Conservation of Nature Red List of Threatened Species). Our predictions, correcting for several quantifiable biases, suggest that 39% of all vascular plant species are threatened with extinction. However, other biases remain unquantified, and may affect our estimate. Preliminary trend data show plants moving toward extinction. Quantitative estimates based on plant extinction risk assessments may understate likely biodiversity loss: they do not fully capture the impacts of climate change, slow‐acting threats, or clustering of extinction risk, which could amplify loss of evolutionary potential. The importance of extinction risk estimation to support existing and emerging conservation initiatives is likely to grow as threats to biodiversity intensify. This necessitates urgent and strategic expansion of efforts toward comprehensive and ongoing assessment of plant and fungal extinction risk.

A process-based ecosystem model (Paleo-BGC) to simulate the dynamic response of Late Carboniferous plants to elevated O2 and aridification

Ecosystem process models provide unique insight into terrestrial ecosystems by employing a modern understanding of ecophysiological processes within a dynamic environmental framework. We apply this framework to deep-time ecosystems made up of extinct plants by constructing plant functional types using fossil remains and simulating—as close as possible—the in vivo response of extinct taxa to their paleoclimatic environment. To accomplish this, foliar characteristics including maximum stomatal conductance, distance from leaf vein to stomata, and cuticular carbon and nitrogen were input as model parameters derived from measurements of well-preserved Pennsylvanian-age fossil leaves. With these inputs, we modeled a terrestrial tropical forest ecosystem dominated by “iconic” plant types of the Pennsylvanian (∼323–299 Ma) including arborescent lycopsids, medullosans, cordaitaleans, and tree ferns using a modified version of the process model BIOME-BGC, which we refer to as Paleo-BGC. Modeled carbon and water—and, for the first time, nitrogen—budgets of a tropical ecosystem from Euramerica driven by daily meteorology are simulated using the Global Circulation Model GENESIS 3.0. Key findings are: lycopsids have the lowest daily leaf water potential, soil water content, surface runoff, and degree of nitrogen leaching indicating an intensive water use strategy compared to medullosans, cordaitaleans, and tree ferns that have increasingly lower simulated water use, greater surface, and nitrogen loss in this order; modeled vegetation response to aridification, which was caused by reduced precipitation and intensified through the close of the Carboniferous and into the Permian shows that lycopsids and medullosans have the lowest tolerance for precipitation decrease compared to cordaitaleans and tree ferns, consistent with the paleobotanical record of occurrence of floral turnovers through the Middle Pennsylvanian through earliest Permian; elevated atmospheric pO2, hypothesized as characteristic for the latter half of the Pennsylvanian and early Permian (∼299–272 Ma), caused higher atmospheric pressure reducing plant transpiration, higher surface water runoff rates, and increased nitrogen export for all plant types simulated, manifested most strongly in the lycopsid dominated ecosystems—with overall only a small reduction in net daily assimilation (≈1 μmol CO2 m−2 s−1). Both aridification and elevated atmospheric oxygen reduced transpiration, increased water retention in soils, with higher surface runoff. With more discharge, enhanced and higher short-term surface soil loss and silicate weathering would have been possible in broad regions of the paleotropics during the late Carboniferous and early Permian. These results are only obtainable by integrating multiple, fossil-derived measurements into the simulation framework of an ecosystem model that utilizes daily meteorology.

Botanic garden solutions to the plant extinction crisis

Social Impact StatementBotanic gardens and arboreta have evolved significantly from their origins as oases reserved for the elite, to the conservation powerhouses they are today, visited by over half a billion people annually. Now, with their sophisticated facilities and botanical expertise, gardens are uniquely positioned to address many of the challenges associated with preserving plant diversity for the benefit of people and the planet. Globally, however, resources for and awareness of these efforts are limited. Funders, governments, corporations, and global citizens need to greatly increase their support of gardens, recognizing the critical role they play in a scientifically informed, coordinated, global effort to save plants from extinction – because all life depends on plants.SummaryOver centuries, botanic gardens and arboreta have evolved considerably in purpose and audience, from a historic focus on teaching and reference collections to championing plant conservation today; gardens fill a major global conservation need at the intersection of horticulture, living collections, plant science, and public education. With a sixth global mass extinction event underway, we are losing plant species before they can even be described, and over 20% of plant species are threatened with extinction. In response to this crisis, gardens are increasingly placing the conservation of plant diversity at the center of their missions, programming, and collections. However, there are significant challenges to preserving the world's vast plant diversity, and plant conservation efforts remain chronically underfunded. We envision a future where gardens have the resources, coordination, and capacity needed to reverse the plant extinction crisis. With sufficient resources, the garden community could: (a) operate an active network of globally coordinated gardens with capacity to carry out integrated plant conservation focused in biodiverse regions; (b) complete threat assessments for all plant species, to inform and prioritize conservation efforts; (c) conserve all “exceptional species” in genetically diverse living collections; and (d) ensure more informed, resilient, and productive landscape restoration efforts are successfully sequestering carbon and supporting biodiversity globally. The garden community is poised to lead these global efforts to preserve and protect plant diversity. Gardens have the expertise, tools, facilities, and networks in place to be the strongest force for plant conservation – they just need the resources to match the global need.

Revealing the diversity of amber source plants from the Early Cretaceous Crato Formation, Brazil

BackgroundAmber has been reported from the Early Cretaceous Crato Formation, as isolated clasts or within plant tissues. Undescribed cones of uncertain gymnosperm affinity have also been recovered with amber preserved in situ. Here, we provide multiple lines of evidence to determine the botanical affinity of this enigmatic, conspicuous cone type, and to better understand the diversity of amber-source plants present in the Crato Formation and beyond.ResultsA new taxon of amber-bearing pollen cone Araripestrobus resinosus gen. nov. et sp. nov. is described here from complete cones and characteristic disarticulated portions. The best-preserved cone portion has both in situ amber infilling the resin canals inside the preserved microsporophyll tissues and pollen of the Eucommiidites-type. This places this genus within the Erdtmanithecales, an incompletely known gymnosperm group from the Mesozoic.FTIR analysis of the in situ amber indicates a potential araucariacean conifer affinity, although affinity with cupressacean conifers cannot be definitely ruled out. Pyr-GC-MS analysis of the Araripestrobus resinosus gen. nov. et sp. nov. in situ fossil resin shows that it is a mature class Ib amber, thought to indicate affinities with araucariacean and cupressacean, but not pinaceous, conifers. This is the first confirmed occurrence of this class of amber in the Crato Formation flora and in South America, except for an archaeological sample from Laguna Guatavita, Colombia.ConclusionsThe combined results of the cones’ novel gross morphology and the analyses of the in situ amber and pollen clearly indicate that the new taxon of resinous gymnosperm pollen cones from the Crato Formation is affiliated with Erdtmanithecales. The cone morphology is very distinct from all known pollen cone types of this extinct plant group. We therefore assume that the plant group that produced Eucommiidites-type pollen is much more diverse in habits than previously thought. Moreover, the diversity of potential amber source plants from the Crato Formation is now expanded beyond the Araucariaceae and the Cheirolepidiaceae to include this member of the Erdtmanithecales. Despite dispersed Eucommiidites pollen being noted from the Crato Formation, this is the first time macrofossils of Erdtmanithecales have been recognized from the Early Cretaceous of South America.

Light absorption and light extinction in barley (Hordeum vulgare L.) as affected by planting dates and plant genotypes

Plant light absorption and extinction may affect plant growth and yield. A split plot experiment (with three replications) was carried out in the Research Field of Agricultural College, Islamic Azad University, Isfahan, Iran, during 2011–2012 in order to determine the influence of light absorption and extinction on barley growth and yield. Planting dates including Oct 10th (P1), 25th (P2), and Nov 10th (P3) and plant genotypes including Nosrat (N), 4Shur (S), and Fajr 30 (F) were used as the main- and sub-plots, respectively. Plant growth and yield as well as crop light absorption and extinction were determined at different growth stages. Using a light meter, the rate of photosynthetically active radiation of canopy in the range of 400–700 nm was determined (41–57%). Light extinction coefficients (0.355–0.485) were also determined according to the Beer-Lambert law. Planting dates and genotypes significantly affected crop growth, yield, and response to light. S resulted in the highest rate of light extinction and absorption at P1 and P3, respectively, and it also resulted in the highest rate of grain yield (4228 kg ha−1) and harvest index (40.9). These results indicated the positive correlation between the growth and yield of barley genotypes with light absorption and extinction. Such findings can be used for a more efficient designing of a barley canopy with higher growth and yield.

Reintroduction approaches and challenges for Cyanea superba (Cham.) A. Gray subsp. superba

Cyanea superba (Cham.) A. Gray subsp. superba is endemic to the island of Oahu in the Hawaiian Islands, and a member of the Campanulaceae family. Cyanea superba subsp. superba was listed endangered on Sept. 11, 1991, and the last in situ plant died in 2002. It is suspected to have been pollinated by nectar-feeding birds and dispersed by frugivorous birds in the past. The U.S. Army’s natural resources program on Oahu began initial reintroduction of this species in 1998 to support its environmental requirements. The program started reintroductions with one field site in the Waianae Mountains, and has since expanded to 20 sites and over 1950 individuals planted, to date. Attempts to recover extinct plant species often require a multifaceted approach, including propagule management, threat control, and reintroduction of the species into field sites. Monitoring results suggest that reintroduction sites outside the historic range of the species have higher overall survival after five years as well as higher seedling survival. Some of the biggest challenges to the reintroduction of C. superba subsp. superba included destruction of habitat from feral pigs, and predation of stems and fruit from rats. Additional threats include invasive weeds, mites and fungal pathogens, as well as predation of seedlings from introduced slugs. Threat control is critical to the establishment and longevity of reintroduction sites. Challenges presented by the material used for restoration and disruptions in plant-animal interactions include a limited number of founder plants as source material, a lack of effective dispersers, and an approximately five year timespan from seed germination to plant maturity in restoration sites.

Inequality in plant diversity knowledge and unrecorded plant extinctions: An example from the grasses of Madagascar

Societal impact statementPlants are essential for all life, providing the infrastructure and energy for our ecosystems. A recent report indicates that more than 500 plant species are already presumed extinct and many more could have been lost without anyone being aware, especially in species‐rich areas with high levels of human impact, and where botanical knowledge is poor. Inequality in the availability and accessibility of biodiversity data, professional expertise, and funding interact to produce chronic differences in knowledge between countries. Here, we illustrate this using an example from Madagascar. Understanding these knowledge inequalities will strengthen our ability to improve the situation for people as well as for plants.SummaryIn order to understand geographic differences in our knowledge of plant extinction, species occurrence knowledge is compared for the grasses (Poaceae) of Madagascar and the British Isles. Poaceae are a useful model system for exploring extinction because they are globally diverse and present interesting characteristics compared with plants as a whole: grasses have a similar species description curve and percentage assessed as threatened, but they have broader and more continental distribution ranges.Historical and current factors affecting the documentation of the Malagasy and British floras are reviewed with regard to science funding, human capital, accessibility, and existing records. Knowledge of Poaceae is compared in the light of these constraints. Global patterns of grass diversity are examined and future extinction rates for Malagasy grasses are estimated.Multiple factors interact to shape a set of constraints on species distribution knowledge. The flora of Madagascar has been described largely by foreigners, science funding is external, and Malagasy botanists face difficult challenges. Spatial data for Madagascar are more limited and less even. We demonstrate that unrecorded extinctions are more likely among Malagasy than British and Irish grasses: they were described later, have smaller ranges, and are more threatened. It is possible that extinction rates of Malagasy grasses will increase tenfold in the next century.Differences in our knowledge of the Malagasy and British floras are long‐standing, deep, and perpetuated by numerous modern‐day factors. We urge researchers to understand and acknowledge these differences, and we provide recommendations for future work.