Increase in crop losses to insect pests in a warming climate Deutsch, Curtis A; Tewksbury, Joshua J; Tigchelaar, Michelle ...
Science (American Association for the Advancement of Science),
08/2018, Letnik:
361, Številka:
6405
Journal Article
Recenzirano
Insect pests substantially reduce yields of three staple grains-rice, maize, and wheat-but models assessing the agricultural impacts of global warming rarely consider crop losses to insects. We use ...established relationships between temperature and the population growth and metabolic rates of insects to estimate how and where climate warming will augment losses of rice, maize, and wheat to insects. Global yield losses of these grains are projected to increase by 10 to 25% per degree of global mean surface warming. Crop losses will be most acute in areas where warming increases both population growth and metabolic rates of insects. These conditions are centered primarily in temperate regions, where most grain is produced.
Paleobiology provides glimpses of future ocean Yasuhara, Moriaki; Deutsch, Curtis A
Science (American Association for the Advancement of Science),
2022-Jan-07, 2022-01-07, 20220107, Letnik:
375, Številka:
6576
Journal Article
Recenzirano
Fossil records from tropical oceans predict biodiversity loss in a warmer world.
Evidence of the distributions of foraminifera over space and time has been compiled in the Triton database, which, as the authors report, enables the detection of changes in the LDG for the past tens ...of millions of years. Because planktonic foraminiferal diversity is correlated with overall biological diversity6, this work might shed light on the mechanisms that underlie the LDG for other groups of organism, too. ...enhanced tropical species richness follows an increased number of closely packed thermal niches from a steeper vertical temperature gradient in cold climates compared with that during warmer periods, an idea long advanced to explain terrestrial tropical diversity in relation to altitude10. ...because deepocean waters obtain their temperature from high-latitude surface waters, ocean circulation translates the global latitude gradient in sea surface temperature into the vertical temperature range of the tropics (Fig. 1). ...a stronger Equator-to-pole gradient in the sea surface temperature in colder climates yields more-variable thermal niches across depth especially in the tropics. Because thermal stratification across water depth also tends to promote sharper oxygen gradients, the diversity-temperature correlations found by Fenton and colleagues might bejointly mediated by the availability of oxygenated habitats.
The average nitrogen-to-phosphorus ratio of marine phytoplankton (16N:1P) is closely matched to the nutrient content of mean ocean waters (14.3N:1P). This condition is thought to arise from ...biological control over the ocean's nitrogen budget, in which removal of bioavailable nitrogen by denitrifying bacteria ensures widespread selection for diazotrophic phytoplankton that replenish this essential nutrient when it limits the growth of other species. Here we show that in the context of a realistic ocean circulation model, and a uniform N:P ratio of plankton biomass, this feedback mechanism yields an oceanic nitrate deficit more than double its observed value. The critical missing phenomenon is diversity in the metabolic N:P requirement of phytoplankton, which has recently been shown to exhibit large-scale patterns associated with species composition. When we model these variations, such that diazotrophs compete with high N:P communities in subtropical regions, the ocean nitrogen inventory rises and may even exceed the average N:P ratio of plankton. The latter condition, previously considered impossible, is prevented in the modern ocean by shallow circulations that communicate stoichiometric signals from remote biomes dominated by diatoms with low N:P ratios. Large-scale patterns of plankton diversity and the circulation pathways connecting them are thus key factors determining the availability of fixed nitrogen in the ocean.
Warming of the oceans and consequent loss of dissolved oxygen (O2) will alter marine ecosystems, but a mechanistic framework to predict the impact of multiple stressors on viable habitat is lacking. ...Here, we integrate physiological, climatic, and biogeographic data to calibrate and then map a key metabolic index—the ratio of O2 supply to resting metabolic O2 demand—across geographic ranges of several marine ectotherms. These species differ in thermal and hypoxic tolerances, but their contemporary distributions are all bounded at the equatorward edge by a minimum metabolic index of ∼2 to 5, indicative of a critical energetic requirement for organismal activity. The combined effects of warming and O2 loss this century are projected to reduce the upper ocean's metabolic index by ∼20% globally and by ∼50% in northern high-latitude regions, forcing poleward and vertical contraction of metabolically viable habitats and species ranges.
Finding forced trends in oceanic oxygen Long, Matthew C.; Deutsch, Curtis; Ito, Taka
Global biogeochemical cycles,
February 2016, 2016-02-00, 20160201, Letnik:
30, Številka:
2
Journal Article
Recenzirano
Odprti dostop
Anthropogenically forced trends in oceanic dissolved oxygen are evaluated in Earth system models in the context of natural variability. A large ensemble of a single Earth system model is used to ...clearly identify the forced component of change in interior oxygen distributions and to evaluate the magnitude of this signal relative to noise generated by internal climate variability. The time of emergence of forced trends is quantified on the basis of anomalies in oxygen concentrations and trends. We find that the forced signal should already be evident in the southern Indian Ocean and parts of the eastern tropical Pacific and Atlantic basins; widespread detection of forced deoxygenation is possible by 2030–2040. In addition to considering spatially discrete metrics of detection, we evaluate the similarity of the spatial structures associated with natural variability and the forced trend. Outside of the subtropics, these patterns are not wholly distinct on the isopycnal surfaces considered, and therefore, this approach does not provide significantly advanced detection. Our results clearly demonstrate the strong impact of natural climate variability on interior oxygen distributions, providing an important context for interpreting observations.
Key Points
Natural variability drives strong fluctuations in dissolved oxygen within the ocean interior
Natural variability challenges detection of forced trends in dissolved oxygen
Time of emergence of forced trends is quantified based on state, trends, and spatial patterns
Ecology. Putting the heat on tropical animals Tewksbury, Joshua J; Huey, Raymond B; Deutsch, Curtis A
Science (American Association for the Advancement of Science),
2008-Jun-06, 20080606, Letnik:
320, Številka:
5881
Journal Article
Nitrogen (N) fixation by diazotrophic plankton is the primary source of this crucial nutrient to the ocean, but the factors limiting its rate and distribution are controversial. According to one ...view, the ecological niche of diazotrophs is primarily controlled by the ocean through internally generated N deficits that suppress the growth of their competitors. A second view posits an overriding limit from the atmosphere, which restricts diazotrophs to regions where dust deposition satisfies their high iron (Fe) requirement, thus separating N sources from sinks at a global scale. Here we use multiple geochemical signatures of N ₂ fixation to show that the Fe limitation of diazotrophs is strong enough to modulate the regional distribution of N ₂ fixation within ocean basins—particularly the Fe-poor Pacific—but not strong enough to influence its partition between basins, which is instead governed by rates of N loss. This scale-dependent limitation of N ₂ fixation reconciles local observations of Fe stress in diazotroph communities with an inferred spatial coupling of N sources and sinks. Within this regime of intermediate Fe control, the oceanic N reservoir would respond only weakly to enhanced dust fluxes during glacial climates, but strongly to the reduced fluxes hypothesized under anthropogenic climate warming.
The impact of anthropogenic climate change on terrestrial organisms is often predicted to increase with latitude, in parallel with the rate of warming. Yet the biological impact of rising ...temperatures also depends on the physiological sensitivity of organisms to temperature change. We integrate empirical fitness curves describing the thermal tolerance of terrestrial insects from around the world with the projected geographic distribution of climate change for the next century to estimate the direct impact of warming on insect fitness across latitude. The results show that warming in the tropics, although relatively small in magnitude, is likely to have the most deleterious consequences because tropical insects are relatively sensitive to temperature change and are currently living very close to their optimal temperature. In contrast, species at higher latitudes have broader thermal tolerance and are living in climates that are currently cooler than their physiological optima, so that warming may even enhance their fitness. Available thermal tolerance data for several vertebrate taxa exhibit similar patterns, suggesting that these results are general for terrestrial ectotherms. Our analyses imply that, in the absence of ameliorating factors such as migration and adaptation, the greatest extinction risks from global warming may be in the tropics, where biological diversity is also greatest.
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