2020 Top 50 Earth, Environmental, and Planetary Sciences Articles

Mapping and quantifying degree of forest modification is critical to conserve and manage forests. Here the authors propose a new quantitative metric for landscape integrity and apply it to a global forest map, showing that less than half of the world’s forest cover has high integrity, most of which is outside nationally designed protected areas.

Tropical rainforests partly create their own climatic conditions by promoting precipitation, therefore rainforest losses may trigger dramatic shifts. Here the authors combine remote sensing, hydrological modelling, and atmospheric moisture tracking simulations to assess forest-rainfall feedbacks in three major tropical rainforest regions on Earth and simulate potential changes under a severe climate change scenario.

Several dams and reservoirs exist along the Nile, most notably the HAD (Egypt) and GERD (Ethiopia) dams. Due to the lack of strategies, the authors here explore potential risks and solutions how to use both dams simultaneously.

Renewable energy production is necessary to mitigate climate change, however, generating the required technologies and infrastructure will demand huge production increases of many metals. Here, the authors map mining areas and assess spatial coincidence with biodiversity conservation sites, and show that new mining threats to biodiversity may surpass those averted by climate change mitigation.

The authors here present a 3D model that simulates the formation of the Chicxulub impact crater. Based on asymmetries in the subsurface structure of the Chicxulub crater, the authors diagnose impact angle and direction and suggest a steeply inclined (60° to horizontal) impact from the northeast.

The Greenland Ice Sheet is the largest land ice contributor to sea level rise and understanding the long-term glacier response to external forcing is key to improved projections. Here the authors show Greenland’s three largest outlet glaciers will likely exceed current worst-case scenario

Forests are critical for stabilizing our climate, but costs of mitigation remain uncertain. Here the authors show the global forest sector could reduce emissions by 6.0 GtCO₂ yr⁻¹ in 2055, or roughly 10% of the mitigation needed to limit warming to 1.5 °C by mid-century, at a cost of 393 billion USD yr⁻¹, or $281/tCO₂.

The potential contribution of Greenland Ice Sheet to sea level rise in the future is known to be substantial. Here, the authors undertake new modelling showing that the Greenland Ice Sheet sea level rise contribution is 7.9 cm more using the CMIP6 SSP585 scenario compared to CMIP5 using multiple RCP8.5 simulations.

Understanding trends in ocean circulation and dynamics is hampered by a lack of long-term records. Here the author uses probabilistic reanalysis of available data to show that transport by the Florida Current has declined over the past 110 years, indicating a slowdown of Atlantic Ocean circulation.

Rare earth elements are used in electronics, but increase in demand could lead to low supply. Here the authors conduct experiments on the International Space Station and show microbes can extract rare elements from rocks at low gravity, a finding that could extend mining potential to other planets.

Reducing soil degradation and improving soil management could make an important contribute to climate change mitigation. Here the authors discuss opportunities and challenges towards implementing a global climate mitigation strategy focused on carbon sequestration in agricultural soils, and propose a framework for guiding region- and soil-specific management options.

The fate of the carbon locked away in soil is uncertain, and there are vast differences between models. Here the authors apply observational, spatio-temporal constraints on carbon turnover projections and find that uncertainty in estimations of carbon dynamics are reduced by 50%.

The risks posed by plastic contamination of the ocean cannot be assessed as their amount and location remain largely unknown. Here the authors show that large quantities of microplastics exist below the ocean surface over the entire Atlantic in quantities greater than previously estimated.

Iron minerals trap carbon in permafrost, preventing microbial degradation and release to the atmosphere as CO₂, but the stability of this carbon as permafrost thaws is unclear. Here the authors use nanoscale analyses to show that thaw conditions stimulate Fe-reducing bacteria that trigger carbon release.

Compound climate events such as floods and droughts together can cause severe socio-economic impacts. Here, the authors analyse global hazard pairs from 1980–2014 and find global hotspots for the occurrence of compound events.

Not all plants are equally able to support native insects. Here, the authors use data on interactions among >12,000 Lepidoptera species and >2000 plant genera across the United States, showing that few plant genera host the majority of Lepidoptera species; this information is used to suggest priorities for plant restoration.

Snow algae bloom along the coast of Antarctica and are likely to be biogeochemically important. Here, the authors produced the first map of such blooms, show that they are driven by warmer temperatures and proximity to birds and mammals, and are likely to increase given projected climate changes.

Marine aquaculture is widely proposed as compatible with ocean sustainability, biodiversity conservation, and human nutrition goals. In this Perspective, Belton and colleagues dispute the empirical validity of such claims and contend that the potential of marine aquaculture has been much exaggerated.

Migration is costly. In the first global analysis of migratory vertebrates, authors report that migratory birds and mammals have faster paces of life than their non-migratory relatives, and that among swimming and walking species, migrants tend to be larger, while among flying species, migrants are smaller.

The disintegration of cryosphere elements such as the Arctic summer sea ice, mountain glaciers, Greenland and West Antarctica is associated with temperature and radiative feedbacks. In this work, the authors quantify these feedbacks and find an additional global warming of 0.43°C.

Ancient impact events on Earth are not well characterized due to continuous re-surfacing of Earth. Here, the authors study impact craters on the Moon with ages up to 800 million years ago and present a cross correlation to Earth, linking up to mass extinction events throughout Earth’s history.

Quantifying forest degradation and biodiversity losses is necessary to inform conservation and restoration policies. Here the authors analyze a large dataset for the Atlantic Forest in South America to quantify losses in forest biomass and tree species richness, functional traits, and conservation value.

There are gaps in international efforts to monitor the wildlife trade, with many species potentially being undetected by the established monitoring groups. Here the authors use an automated web search to document the sale of reptiles online, revealing over 36% of all known reptile species are in trade, including many missing from official databases.

Historically it has been maintained that soil organic carbon (SOC) is stabilized through interactions with mineral interfaces. Here the authors use cryo-electron microscopy and spectroscopy to show that SOC interactions can also occur between organic forms in patchy, disordered structure.

Plastic pollution is a critical concern across diverse ecosystems, yet most research has focused on terrestrial and aquatic transport, neglecting other mechanisms. Here the authors show that atmospheric transport is a major pathway for road plastic pollution over remote regions.

This study makes use of the total spread of zircon ages and trace elements to study the thermal evolution of magmatic systems. Applied to Nevado de Toluca, the authors determine the size of its subvolcanic magma reservoir and assess its potential of re-activation.

Ocean uptake of carbon dioxide impacts the climate, but flux estimates from surface measurements have not been corrected for temperature differences between surface and water sampling depth. Making that correction, the authors find previous estimates for ocean uptake have been substantially underestimated.

Zooplankton biomass in the dark ocean is thought to be low and weakly coupled to epipelagic primary production, but recent evidence suggests otherwise. Here the authors analyse data from the Malaspina Circumnavigation Expedition and published data to estimate bathypelagic zooplankton biomass and assess its relationship to primary production, currently not well accounted for in oceanic C budget.

The effectiveness of protected areas depends not only on whether they are intact, but also on whether they are mutually connected. Here the authors examine the structural connectivity of terrestrial protected areas globally, finding that less than 10% of the protected network can be considered connected.

The ~70 km-diameter Yarrabubba impact structure in Western Australia has previously been regarded as among Earth’s oldest meteorite craters, but has hitherto lacked absolute age constraints. Here, the authors determine a precise impact age of 2229 ± 5 Ma, which extends the terrestrial cratering record back in time by > 200 million years and establishes Yarrabubba as the oldest recognised meteorite impact structure on Earth.

Phosphorus is an essential nutrient critical for agriculture, but because it is non-renewable its future availability is threatened. Here the authors show that across the globe most nations have net losses of phosphorus, with soil erosion as the major route of loss in Europe, Africa and South America.

Local human activities can lead to cross-border environmental impacts through the food–energy–water–CO₂ nexus. Here, the authors report wide variations in environmental impacts of irrigated agriculture across counties within the North China Plain under different environmental and socioeconomic scenarios.

Cichlids are a model for adaptive radiation, but the timing of their diversification is debated. Here the authors assemble 14 cichlid genomes, introduce a Bayesian approach to account for fossil-assignment uncertainty, and present a dated phylogenomic hypothesis of cichlid and teleost evolution.

The fate of subducted CO₂ remains debated, with estimates mainly from numerical predictions varying from wholesale decarbonation of the shallow subducting slab to massive deep subduction of CO₂. Here, the authors present field-based data and show that ~40% to ~65% of the CO₂ in subducting crust is released via metamorphic decarbonation reactions at forearc depths.

The causes of the Upper Pleistocene megafauna extinction in Australia and New Guinea are debated, but fossil data are lacking for much of this region. Here, Hocknull and colleagues report a new, diverse megafauna assemblage from north-eastern Australia that persisted until ~40,000 years ago.

Excess fertilizer use causes subsurface contamination. Here, the authors conduct an assessment of water quality vulnerability across Europe, finding that 75% of agricultural regions are susceptible to nitrate contamination for least one-third of the year, two times more than using standard estimation procedure.

The authors here present a deep learning model that simultaneously detects earthquake signals and measures seismic-phase arrival times. The model performs particularly well for cases with high background noise and the challenging task of picking the S wave arrival.

A Southern Ocean influences on the carbon cycle is considered a key component of deglacial changes. Here, the authors show spatial differences in glacial Southern Ocean carbon storage that dissipated rapidly 14.6 kyr ago, revealing a South Indian Ocean contribution to rapid deglacial atmospheric CO₂ increases.

Strong mitigation of anthropogenic emissions is necessary, but it is not clear how fast these efforts would lead to temperature changes. Here, the authors find that there is a substantial delay between reductions of emissions and a detectable change in surface temperature for a number of climate forcers.

Human activities have accelerated soil erosion and landscape change in many areas. Here the authors show how rates of erosion, sediment transfer and alluvial sedimentation have increased by an order of magnitude across North America since European colonization, far exceeding the rates expected of natural processes.

How Earth’s lithosphere first divided into tectonic plates remains uncertain. Here, the authors use 3D spherical shell models to demonstrate that anticipated warming of the early lithosphere should lead to thermal expansion and the initiation of a global network of rifts, dividing the lithosphere into tectonic plates.

Soil age is thought to be an important driver of ecosystem development. Here, the authors perform a global survey of soil chronosequences and meta-analysis to show that, contrary to expectations, soil age is a relatively minor ecosystem driver at the biome scale once other drivers such as parent material, climate, and vegetation type are accounted for.

Pegmatite crystals are thought to grow rapidly, yet their growth rates and conditions are not well constrained. Here, the authors find that the trace element distributions of pegmatitic quartz crystals indicate rapid growth in highly dynamic environments, suggesting that large meter-scale crystals can be formed within days.

Little is known about how the speed of ecosystem collapse depends on ecosystem size. Here, Cooper, Willcock et al. analyse empirical data and models finding that although regime shift duration increases with ecosystem size, this relationship saturates and even large ecosystems can collapse in a few decades.

Due to legislative shortfalls, species of global conservation concern can still be captured in commercial fisheries. Here the authors show that 91 threatened species are reported in catch/landing databases, 13 of which are traded internationally despite their conservation concern.

Conversion of natural ecosystems to cropland is a threat to most native wildlife. Here the authors quantify the impact of recent cropland expansion on the habitat of representative pollinator, bird, plant species across the conterminous United States, showing diminished crop yield returns at the cost of important habitat losses.

It is generally difficult to scale derived estimates and understand the accuracy across locations for passively-collected data sources, such as mobile phones and satellite imagery. Here the authors show that their trained deep learning models are able to explain 70% of the variation in ground-measured village wealth in held-out countries, outperforming previous benchmarks from high-resolution imagery with errors comparable to that of existing ground data.

Dryness stresses vegetation and can lead to declines in productivity, increased emission of carbon, and plant mortality, but the drivers of this stress remain unclear. Here the authors show that soil moisture plays a dominant role relative to atmospheric water demand over most global land vegetated areas.

Adequate water availability is key to human and ecosystem sustainability. Here, the authors show that seasonally variable regimes become more variable, and the combined influence of seasonality and magnitude of climate variables will affect future water availability.

The impact on inadequate water quality on water scarcity is unclear. Here the authors quantify China’s present-day water scarcity and show that inadequate water quality exacerbates China’s water scarcity, which is unevenly distributed across the country.

Here the authors develop a set of global, long-term, spatial projections of urban land expansion for understanding the planet’s potential urban futures. The global total amount of urban land increases by a factor of 1.8-5.9 over the 21st century, and the developed world experiences as much new urban development as the developing world.