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Satellites and other remote sensing tools offer new ways to study ecosystems—and maybe even save them

Lose the tusks Harvest and poaching of wildlife have increased as the human population and our technology have grown. These pressures now occur on such a scale that they can be considered selective drivers. Campbell-Staton et al . show that this phenomenon has occurred in African elephants, which are poached for their ivory, during the 20-year Mozambican civil war (see the Perspective by Darimont and Pelletier). In response to heavy poaching by armed forces, African elephant populations in Gorongosa National Park declined by 90%. As the population recovered after the war, a relatively large proportion of females were born tuskless. Further exploration revealed this trait to be sex linked and related to specific genes that generated a tuskless phenotype more likely to survive in the face of poaching. —SNV

Molecular time trees indicating that embryophytes originated around 500 million years ago (Ma) during the Cambrian are at odds with the record of fossil plants, which first appear in the mid-Silurian almost 80 million years later. This time gap has been attributed to a missing fossil plant record, but that attribution belies the case for fossil spores. Here, we describe a Tremadocian (Early Ordovician, about 480 Ma) assemblage with elements of both Cambrian and younger embryophyte spores that provides a new level of evolutionary continuity between embryophytes and their algal ancestors. This finding suggests that the molecular phylogenetic signal retains a latent evolutionary history of the acquisition of the embryophytic developmental genome, a history that perhaps began during Ediacaran-Cambrian time but was not completed until the mid-Silurian (about 430 Ma).

Birds in the bin It is by now well accepted that humans are not the only animal to have complex culture, and we have also found that ecological novelty can lead to cultural innovation. Klump et al. documented the emergence of an evolving set of behaviors in response to human-generated resources, specifically garbage bins, in sulphur-crested cockatoos. This finding both documents the existence and spread of complex foraging culture among parrots, a lineage known for high-level cognitive function, and illuminates how the spread of a cultural innovation can lead to regional distinct variations. Science , abe7808, this issue p. 456

Channeling carbon dioxide The separation of gas molecules with physisorbents can be challenging because there is often a tradeoff between capacity and selectivity. Zhou et al. report a template-free hydrothermal synthesis of the one-dimensional channel zeolite mordenite, in which some silicon was replaced by iron. Rather than forming a powder that requires further shaping, this mechanically stable material self-assembled into monoliths. Iron atoms bound in tetrahedral zeolite sites narrowed the channels and enabled the size-exclusion separation of carbon dioxide (CO 2 ) over nitrogen (N 2 ) and methane. High CO 2 uptake and highly efficient CO 2 –N 2 separation was demonstrated for both dry and humid conditions. Science , aax5776, this issue p. 315

The limits of channel offset The offset of stream channels across a strike-slip fault offer a record of long-term slip rates. The process itself is an interesting case of landscape evolution because the streams will spill straight across the fault at some point and reset the offset. Dascher-Cousineau et al. developed a model for this process that they validated using observations from the Carrizo Plain in California. The model leverages transitions from active to abandoned stream channels to determine when and how drainage networks in these regions reorganize and allow quantification of both slip and bedload transport. Science , abf2320, this issue p. 204

Human activities are changing our environment. Along with climate change and a widespread loss of biodiversity, plastic pollution now plays a predominant role in altering ecosystems globally. Here, we review the occurrence of plastic ingestion by wildlife through evolutionary and ecological lenses and address the fundamental question of why living organisms ingest plastic. We unify evolutionary, ecological, and cognitive approaches under the evolutionary trap theory and identify three main factors that may drive plastic ingestion: (i) the availability of plastics in the environment, (ii) an individual’s acceptance threshold, and (iii) the overlap of cues given by natural foods and plastics.

The shrinking solution space for adaptation calls for long-term dynamic planning starting now

The rate of global sea level rise is increasing as ice from Greenland and Antarctica melts and warmer seawater expands. By 2050, sea levels could surge by 10 to 25 millimeters per year, according to climate modelers, up from just about 3 millimeters per year now. The rising water could drown some 20% to 90% of the world9s coastal wetlands, destroying habitats that are among the most ecologically valuable on Earth. But coastal scientist Matt Kirwan has argued that such forecasts of wetland loss are needlessly bleak. Studies he and his colleagues have conducted suggest some tidal wetlands can keep pace with sea level rise, by building their soils vertically and migrating inland horizontally as water creeps up coastlines. Some coastal wetlands could even expand, if people don9t block their paths with seawalls or other infrastructure. But many researchers are skeptical of Kirwan9s findings, and have begun to challenge his work.

Think globally, act locally Climate change–driven elevations in temperature over the past few decades have caused repeated coral bleaching and subsequent death. The impact is so widespread that it has been suggested that only climate change reversal can save coral reefs globally. Donovan et al. looked at the interaction between local conditions and coral reef health and found that poor conditions magnify climate impacts (see the Perspective by Knowlton). Furthermore, reefs where human stressors such as overfishing or pollution were minimized fared better. Such results suggest that caring for reefs locally may help them to persist in our warming world. Science , abd9464, this issue p. 977 ; see also abi7286, p. 908

The pace of Holocene vegetation change Although much is known about the rapid environmental changes that have occurred since the Industrial Revolution, the patterns of change over the preceding millennia have been only patchily understood. Using a global set of >1100 fossil pollen records, Mottl et al. explored the rates of vegetation change over the past 18,000 years (see the Perspective by Overpeck and Breshears). The authors show that the rates of change accelerated markedly during the Late Holocene (∼4.6 to 2.9 thousand years ago), even more rapidly than the climate-driven vegetation changes associated with the end of the last glacial period. In addition, the Late Holocene acceleration began for terrestrial communities as a whole, suggesting that the acceleration in turnover over the past two centuries is the tip of a deeper trend. Science , abg1685, this issue p. 860 ; see also abi9902, p. 786

When your well runs dryGroundwater provides nearly half of the water used for agricultural irrigation and most of the drinking water for billions of people. It is essential, then, for this resource to remain secure. Jasechko and Perrone examined data from approximately 39 million wells in 40 countries worldwide to investigate their vulnerability to declining water levels (see the Perspective by Famiglietti and Ferguson). The authors found that construction of deeper wells is not occurring in some areas that are experiencing groundwater decline, a disconnect that poses risks for people who rely on well water.Science, this issue p.418; see also p.344

In Louisiana, state officials and scientists are working to harness the Mississippi River to save part of the coast from disappearing into the Gulf of Mexico. The project, billed as one of the world9s largest ecological restoration efforts, is a grand experiment in trying to revive some of the natural processes that built Louisiana9s rich coastal wetlands. The plan calls for routing part of the sediment-filled river into nearby Barataria Bay, just south of New Orleans. The hope is this new sand and mud will replenish marshes starved of sediment when the river was walled off by a network of levees decades ago. Scientists who have documented the coast9s decline are now working to understand what9s likely to happen if the river is unleashed, and to document the effects if the project goes forward.

Backtracking a pandemic Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) may have had a history of abortive human infections before a variant established a productive enough infection to create a transmission chain with pandemic potential. Therefore, the Wuhan cluster of infections identified in late December of 2019 may not have represented the initiating event. Pekar et al. used genome data collected from the early cases of the COVID-19 pandemic combined with molecular clock inference and epidemiological simulation to estimate when the most successful variant gained a foothold in humans. This analysis pushes human-to-human transmission back to mid-October to mid-November of 2019 in Hubei Province, China, with a likely short interval before epidemic transmission was initiated. Science, this issue p. 412, SARS-CoV-2 human-to-human transmission likely initiated in mid-October to mid-November 2019 in Hubei, China., Understanding when severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) emerged is critical to evaluating our current approach to monitoring novel zoonotic pathogens and understanding the failure of early containment and mitigation efforts for COVID-19. We used a coalescent framework to combine retrospective molecular clock inference with forward epidemiological simulations to determine how long SARS-CoV-2 could have circulated before the time of the most recent common ancestor of all sequenced SARS-CoV-2 genomes. Our results define the period between mid-October and mid-November 2019 as the plausible interval when the first case of SARS-CoV-2 emerged in Hubei province, China. By characterizing the likely dynamics of the virus before it was discovered, we show that more than two-thirds of SARS-CoV-2like zoonotic events would be self-limited, dying out without igniting a pandemic. Our findings highlight the shortcomings of zoonosis surveillance approaches for detecting highly contagious pathogens with moderate mortality rates.

The birth of modern rainforestsThe origin of modern rainforests can be traced to the aftermath of the bolide impact at the end of the Cretaceous. Carvalhoet al.used fossilized pollen and leaves to characterize the changes that took place in northern South American forests at this time (see the Perspective by Jacobs and Currano). They not only found changes in species composition but were also able to infer changes in forest structure. Extinctions were widespread, especially among gymnosperms. Angiosperm taxa came to dominate the forests over the 6 million years of recovery, when the flora began to resemble that of modern lowland neotropical forest. The leaf data also imply that the forest canopy evolved from relatively open to closed and layered, leading to increased vertical stratification and a greater diversity of plant growth forms.Science, this issue p.63; see also p.28

A volcanic source of variationThe Atlantic Multidecadal Oscillation (AMO), a 50- to 70-year quasiperiodic variation of climate centered in the North Atlantic region, was long thought to be an internal oscillation of the climate system. Mannet al.now show that this variation is forced externally by episodes of high-amplitude explosive volcanism. They used an ensemble of climate models to evaluate the causes of the AMO, finding that volcanos are the most important influence, and that there is no evidence to show that it has been internally generated during the last millennium.Science, this issue p.1014

Warming autumns, fewer butterfliesMany recent studies have revealed sweeping declines in insects over the past few decades. Butterflies are no exception. Foristeret al.used three different datasets, collected by both experts and community scientists, and found that the number of butterflies has declined over the past 40 years. Although the drivers of decline are complex, the authors found that climate change—in particular, warmer months in the autumn—explain a large portion, even as warming summers actually lead to increases. This work shows that climate change impacts may be insidious and unexpected in their effects.Science, this issue p.1042

What matters for mudrocks Rock such as slate and shale, which form from mud, suddenly start appearing in the geologic record around 450 million years ago. Their appearance at about the same time as certain plants seems to implicate plant roots in the formation of these ubiquitous rocks. Zeichner et al. found a different route for creating the flocculation required for mudrock. Using analog experiments, the authors found that organic matter from plants alone was sufficient for the formation of flocs—aggregates of small silt and clay particles—which are required to deposit mudrock. This observation could explain the appearance of these rocks in places where the plants did not have deep roots. Science , this issue p. 526

The long-term effects of climate change on biodiversity and biogeographic patterns are uncertain. There are known relationships between geographic area and both the number of species and the number of ecological functional groups-termed the species-area relationship and the functional diversity-area relationship, respectively. We show that there is a positive relationship between the number of species in an area, the number of ecological functional groups, and oceanic temperature in the shallow-marine fossil record of New Zealand over a time span of ~40 million years. One implication of this relationship is that functional redundancy increases with temperature. This reveals a long-lived and persistent association between the spatial structuring of biodiversity, the temperature-dependence of functional redundancy, and shallow-marine biodiversity in mid-latitudes.

A shared Earth approach links biodiversity and people

Songbirds reclaim favored frequencies When severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic lockdowns were instituted across entire countries, human activities ceased in an unprecedented way. Derryberry et al. found that the reduction in traffic sound in the San Francisco Bay Area of California to levels not seen for half a century led to a shift in song frequency in white-crowned sparrows (see the Perspective by Halfwerk). This shift was especially notable because the frequency of human-produced traffic noise occurs within a range that interferes with the highest performance and most effective song. Thus, our “quiet” allowed the birds to quickly fill the most effective song space. Science , this issue p. 575 ; see also p. 523

Origins of an alpine flora The evolution of high mountain floras is strongly influenced by tectonic and climatic history. Ding et al. document the timing, tempo, and mode by which the world's most species-rich alpine flora, that of the Tibet-Himalaya-Hengduan region, was assembled. Alpine assemblages in the region are older than previously thought, with lineages tracing their alpine ancestry to the early Oligocene—older than any other modern alpine system. Alpine species diversified faster during periods of orogeny and intensification of the Asian monsoon, and the Hengduan Mountains—the most species-rich area in this region—played a key biogeographic role as the location of the earliest pulse of alpine diversification in the Oligocene. Science , this issue p. 578

A genetic history of China The history of human movements into and within China has been difficult to determine solely from archaeological investigations or genetic studies of contemporary peoples. Yang et al. sequenced DNA from 26 individuals from 9500 to 300 years ago from locations within China. Analyses of these individuals, along with previously sequenced ancient individuals and present-day genomes representing global populations, show a split between ancient humans in northern and southern China. Neolithic northern Chinese individuals are closest to modern-day East Asians, whereas ancient individuals from southern China are most closely related to modern-day Southeast Asians and show an affinity to modern-day Austronesian populations. These results indicate that there was a southward movement and admixture of peoples during the Neolithic that gave rise to modern-day populations in East Asia. Science this issue p. 282

Food for thought Phytoplankton abundances in the Arctic Ocean have been increasing over recent decades as the region has warmed and sea ice has disappeared. The presumptive causes of this increase were expanding open water area and a longer growing season—at least until now. Lewis et al. show that although these factors may have driven the productivity trends before, over the past decade, phytoplankton primary production rose by more than half because of increased phytoplankton concentrations (see the Perspective by Babin). This finding means that there has been an influx of new nutrients into the region, suggesting that the Arctic Ocean could become more productive and export additional carbon in the future. Science , this issue p. 198 ; see also p. 137

A plant-herbivore information “arms race” The consumption of plants by herbivores has driven the evolution of many diverse plant defense chemicals to which herbivores have constantly adapted. The transmission of chemical information at the community level is less known but important given the plethora of plant and herbivore species, especially in tropical communities. Zu et al. propose an information “arms race” approach to explain plant-herbivore chemical communication at the community level (see the Perspective by Solé). To test their conceptual framework, they used field data of herbivore-plant interactions and plant–volatile organic compound associations in a tropical dry forest. Their approach provides an understanding of the functioning and persistence of systems where individuals send and receive information in the form of signals to which other individuals react and, in turn, affect the behavior of other participants in these systems. Science , this issue p. 1377 ; see also p. 1315

Taking stock of our losses Earth's ice sheets are melting and sea levels are rising, so it behooves us to understand better which climate processes are responsible for how much of the mass loss. Smith et al. estimated grounded and floating ice mass change for the Greenland and Antarctic ice sheets from 2003 to 2019 using satellite laser altimetry data from NASA's ICESat and ICESat-2 satellites. They show how changing ice flow, melting, and precipitation affect different regions of ice and estimate that grounded-ice loss averaged close to 320 gigatons per year over that period and contributed 14 millimeters to sea level rise. Science , this issue p. 1239

The Caribbean was one of the last regions of the Americas to be settled by humans, but where they came from and how and when they reached the islands remain unclear. We generated genome-wide data for 93 ancient Caribbean islanders dating between 3200 and 400 calibrated years before the present and found evidence of at least three separate dispersals into the region, including two early dispersals into the Western Caribbean, one of which seems connected to radiation events in North America. This was followed by a later expansion from South America. We also detected genetic differences between the early settlers and the newcomers from South America, with almost no evidence of admixture. Our results add to our understanding of the initial peopling of the Caribbean and the movements of Archaic Age peoples in the Americas., The research was funded by the Max Planck Society and the European Research Council under the 7th Framework Program (grant agreement no. 319209, ERC Synergy Project NEXUS1492). H.S. was supported by the HERA (Humanities in the European Research Area) Joint Research Program “Uses of the Past” (CitiGen) and the European Union’s Horizon 2020 research and innovation program under grant agreement no. 649307. W.J.P. and M.A.N.-C. were supported by the National Science Foundation (BCS-0612727 and BCS1622479). C.L.-F. was supported by a grant from the Ministry of Science, Innovation and Universities (PGC2018-0955931-B-100, AEI/FEDER, UE). M.R. was supported by the Social Sciences and Humanities Research Council of Canada (435-2016-0529). M.R., Y.C.d.A., U.M.G.H., and S.T.H.G. were supported by the Social Sciences and Humanities Research Council of Canada (standard research grant SSHRC ‐ 410‐2011‐1179 and SSHRC postdoctoral fellowship ‐ 756‐2016‐0180) and several University of Winnipeg internal grants (Major grant 2017, 2018; Partnership Development grant 2017, 2018; and Discretionary grant 2017, 2018).

A rapid retreat Are the rates at which we observe ice shelves shrinking today representative of how fast they shrank in the past? Dowdeswell et al. report observations of the Antarctic seafloor that reveal the presence of submarine grounding-zone wedges on the Larsen continental shelf (see the Perspective by Jakobsson). The authors interpret these ridges as being caused by the tidal rise and fall of the ice shelf at the grounding line, which squeezes the underlying sediments when it rests on the seafloor. From this, they calculated that ice shelf retreat at this location about 14,000 years ago was at times as much as 100 times as fast as the average over the past 10,000 years. Science , this issue p. 1020 ; see also p. 939

Rumblings of a dormant volcano Earthquakes near volcanoes are often a warning sign of a future eruption. However, deep long-period earthquakes (DLPs) are a special type of seismicity tied most often to quiescent volcanoes. Wech et al. found more than a million of these DLPs under the inactive Mauna Kea volcano in Hawai'i over the past 19 years (see the Perspective by Matoza). Analysis of this large number of observations allowed the authors to conclude that the DLPs were connected to a deep, cooling magma body. Deep gas releases triggered by minerals crystallizing in the deep magma through the “second boiling” process may open cracks, triggering the DLPs. Science , this issue p. 775 ; see also p. 708

A South American anthropoid Although there are many primate lineages in the Old World, it is thought that the New World is home to just one group, the platyrrhine monkeys, which appear to have colonized the region during the Eocene. Seiffert et al. describe a new primate species on the basis of fossil molars found in the Peruvian Amazon that appears to belong to the Parapithecidae, a group of stem anthropoid primates best known from northern Africa (see the Perspective by Godinot). The fossils appear to be from a well-differentiated lineage, suggesting that this species had been evolving within South America for some time. It is likely that the ancestors of this new species arrived via a transatlantic rafting event when sea levels dropped at the Eocene–Oligocene transition ∼32 to 35 million years ago. Science , this issue p. 194 ; see also p. 136

Not a big deal after all Do volcanic eruptions affect El Niño–Southern Oscillation (ENSO) variability? Models indicate that sulfate aerosols resulting from large eruptions can initiate an El Niño–like response in the tropical Pacific, but observations have not shown evidence of such behavior. Dee et al . present an oxygen-isotope time series of fossil corals from the central tropical Pacific to investigate ENSO's response to large volcanic eruptions during the past millennium. They found a weak tendency for an El Niño–like response in the year after an eruption, but not one that was statistically significant. These results suggest that large volcanic events have not triggered a detectable response in ENSO over the past thousand years and that their impact is small relative to the degree of natural variability. Science , this issue p. 1477

The Antarctic Ice Sheet is losing mass at an accelerating pace, and ice loss will likely continue over the coming decades and centuries. Some regions of the ice sheet may reach a tipping point, potentially leading to rates of sea level rise at least an order of magnitude larger than those observed now, owing to strong positive feedbacks in the ice-climate system. How fast and how much Antarctica will contribute to sea level remains uncertain, but multimeter sea level rise is likely for a mean global temperature increase of around 2°C above preindustrial levels on multicentennial time scales, or sooner for unmitigated scenarios., info:eu-repo/semantics/published

The Southern Ocean exerts a major influence on the mass balance of the Antarctic Ice Sheet, either indirectly, by its influence on air temperatures and winds, or directly, mostly through its effects on ice shelves. How much melting the ocean causes depends on the temperature of the water, which in turn is controlled by the combination of the thermal structure of the surrounding ocean and local ocean circulation, which in turn is determined largely by winds and bathymetry. As climate warms and atmospheric circulation changes, there will be follow-on changes in the ocean circulation and temperature. These consequences will affect the pace of mass loss of the Antarctic Ice Sheet.

Antarctica contains most of Earth’s fresh water stored in two large ice sheets. The more stable East Antarctic Ice Sheet is larger and older, rests on higher topography, and hides entire mountain ranges and ancient lakes. The less stable West Antarctic Ice Sheet is smaller and younger and was formed on what was once a shallow sea. Recent observations made with several independent satellite measurements demonstrate that several regions of Antarctica are losing mass, flowing faster, and retreating where ice is exposed to warm ocean waters. The Antarctic contribution to sea level rise has reached ~8 millimeters since 1992. In the future, if warming ocean waters and increased surface meltwater trigger faster ice flow, sea level rise will accelerate.

Dating the arrival of the first hominins in Java The World Heritage archaeological site at Sangiran on the island of Java in Indonesia has major importance for the understanding of human arrival and evolution in Asia. However, the timing of the first appearance of Homo erectus at the site has been controversial. Using a combination of dating techniques for hominin-bearing sediments, Matsu'ura et al. resolved the arrival of H. erectus at ∼1.3 million years ago (see the Perspective by Brasseur). This dating suggests that the earliest hominins in Sangiran are at least 200,000 years younger than has been thought and may represent an important step to the resolution of the controversy. Science , this issue p. 210 ; see also p. 147

Hershkovitz et al . (Reports, 25 June 2021, p. 1424) conclude that the Nesher Ramla (NR) fossils represent a distinctive Homo paleodeme that played a role as a source population for Neanderthals. However, the highly diagnostic features of the Neanderthal mandible—clearly displayed by the NR fossils—are largely overlooked. Our analyses indicate that the NR fossils represent simply a Neanderthal.

What are the full extent and long-term effects of land dispossession and forced migration for Indigenous peoples in North America? We leveraged a new dataset of Indigenous land dispossession and forced migration to statistically compare features of historical tribal lands to present-day tribal lands at the aggregate and individual tribe level. Results show a near-total aggregate reduction of Indigenous land density and spread. Indigenous peoples were forced to lands that are more exposed to climate change risks and hazards and are less likely to lie over valuable subsurface oil and gas resources. Agricultural suitability and federal land proximity results—which affect Indigenous movements, management, and traditional uses—are mixed. These findings have substantial policy implications related to heightened climate vulnerability, extensive land reduction, and diminished land value.

Understanding the response of Himalayan-Karakoram (HK) rivers to climate change is crucial for ~1 billion people who partly depend on these water resources. Policy-makers tasked with sustainable water resources management require an assessment of the rivers' current status and potential future changes. We show that glacier and snow melt are important components of HK rivers, with greater hydrological importance for the Indus basin than for the Ganges and Brahmaputra basins. Total river runoff, glacier melt, and seasonality of flow are projected to increase until the 2050s, with some exceptions and large uncertainties. Critical knowledge gaps severely affect modeled contributions of different runoff components, future runoff volumes, and seasonality. Therefore, comprehensive field observation-based and remote sensing-based methods and models are needed.

Hansson et al . argue that our main finding could provide an overly simplistic metric for maximizing genetic rescue. They agree that translocating the most genetically diverse individuals led to a large increase in translocated tortoise survival, but recommend instead moving individuals that have low genetic load and the greatest representation of metapopulation diversity. Their recommendation is based on specific model assumptions and fitness effects that are often unknown and are not generalizable to many endangered species applications.

Spatial structure of species change Biodiversity is undergoing rapid change driven by climate change and other human influences. Blowes et al. analyze the global patterns in temporal change in biodiversity using a large quantity of time-series data from different regions (see the Perspective by Eriksson and Hillebrand). Their findings reveal clear spatial patterns in richness and composition change, where marine taxa exhibit the highest rates of change. The marine tropics, in particular, emerge as hotspots of species richness losses. Given that human activities are affecting biodiversity in magnitudes and directions that differ across the planet, these findings will provide a much needed biogeographic understanding of biodiversity change that can help inform conservation prioritization. Science , this issue p. 339 ; see also p. 308

The future of nature's contributions A recent Global Assessment by the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services has emphasized the urgent need to determine where and how nature's contribution matters most to people. Chaplin-Kramer et al. have developed a globalscale modeling of ecosystem services, focusing on water quality regulation, coastal protection, and crop pollination (see the Perspective by Balvanera). By 2050, up to 5 billion people may be at risk from diminishing ecosystem services, particularly in Africa and South Asia. Science , this issue p. 255 ; see also p. 184

A heavy toll Trade in wildlife, and their parts, is well recognized for a few key species, such as elephants and rhinos, but it occurs globally, across a wide array of species. Scheffers et al. looked across tens of thousands of vertebrate species and found that one in every five species is affected by trade of some sort. The impacts of trade tend to be concentrated in certain phylogenetic groups, thus the potential for long-term impact on certain lineages is substantial. This analysis allows for prediction of potential for trade where it does not yet occur, facilitating proactive prevention. Science , this issue p. 71

Staggering decline of bird populations Because birds are conspicuous and easy to identify and count, reliable records of their occurrence have been gathered over many decades in many parts of the world. Drawing on such data for North America, Rosenberg et al. report wide-spread population declines of birds over the past half-century, resulting in the cumulative loss of billions of breeding individuals across a wide range of species and habitats. They show that declines are not restricted to rare and threatened species—those once considered common and wide-spread are also diminished. These results have major implications for ecosystem integrity, the conservation of wildlife more broadly, and policies associated with the protection of birds and native ecosystems on which they depend. Science , this issue p. 120

Invisible threat Our changing climate is a threat to corals, causing disfiguring bleaching and mortality to reefs that once teemed with life. Shlesinger and Loya alert us to an equally dangerous yet nearly invisible hazard to coral: loss of breeding synchrony (see the Perspective by Fogarty and Marhaver). They found that environmental changes have resulted in shifts in the timing of gamete release in several species of broadcast-spawning corals in the Red Sea. Similar changes are likely occurring globally. Such a loss of spawning synchrony could result in reproductive failure, a much less obvious but no less insidious threat to coral reefs. Science , this issue p. 1002 ; see also p. 987