Exposure to elevated concentrations of surface ozone (O
3) causes substantial reductions in the agricultural yields of many crops. As emissions of O
3 precursors rise in many parts of the world over ...the next few decades, yield reductions from O
3 exposure appear likely to increase the challenges of feeding a global population projected to grow from 6 to 9 billion between 2000 and 2050. This study estimates year 2000 global yield reductions of three key staple crops (soybean, maize, and wheat) due to surface ozone exposure using hourly O
3 concentrations simulated by the Model for Ozone and Related Chemical Tracers version 2.4 (MOZART-2). We calculate crop losses according to two metrics of ozone exposure – seasonal daytime (08:00–19:59) mean O
3 (M12) and accumulated O
3 above a threshold of 40 ppbv (AOT40) – and predict crop yield losses using crop-specific O
3 concentration:response functions established by field studies. Our results indicate that year 2000 O
3-induced global yield reductions ranged, depending on the metric used, from 8.5–14% for soybean, 3.9–15% for wheat, and 2.2–5.5% for maize. Global crop production losses totaled 79–121 million metric tons, worth $11–18 billion annually (USD
2000). Our calculated yield reductions agree well with previous estimates, providing further evidence that yields of major crops across the globe are already being substantially reduced by exposure to surface ozone – a risk that will grow unless O
3-precursor emissions are curbed in the future or crop cultivars are developed and utilized that are resistant to O
3.
► Surface O
3 is having a substantial impact on the yields of key crops. ► Yields of wheat, soybean, and maize were reduced by up to 15% globally in 2000. ► Global year 2000 crop production losses totaled 79–121 million metric tons. ► Agricultural losses are estimated to be worth $11–18 billion USD
2000 annually.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
We examine the potential global risk of increasing surface ozone (O
3) exposure to three key staple crops (soybean, maize, and wheat) in the near future (year 2030) according to two trajectories of O
...3 pollution: the Intergovernmental Panel on Climate Change Special Report on Emissions Scenarios (IPCC SRES) A2 and B1 storylines, which represent upper- and lower-boundary projections, respectively, of most O
3 precursor emissions in 2030. We use simulated hourly O
3 concentrations from the Model for Ozone and Related Chemical Tracers version 2.4 (MOZART-2), satellite-derived datasets of agricultural production, and field-based concentration:response relationships to calculate crop yield reductions resulting from O
3 exposure. We then calculate the associated crop production losses and their economic value. We compare our results to the estimated impact of O
3 on global agriculture in the year 2000, which we assessed in our companion paper Avnery et al., 2011. In the A2 scenario we find global year 2030 yield loss of wheat due to O
3 exposure ranges from 5.4 to 26% (a further reduction in yield of +1.5–10% from year 2000 values), 15–19% for soybean (reduction of +0.9–11%), and 4.4–8.7% for maize (reduction of +2.1–3.2%) depending on the metric used, with total global agricultural losses worth $17–35 billion USD
2000 annually (an increase of +$6–17 billion in losses from 2000). Under the B1 scenario, we project less severe but still substantial reductions in yields in 2030: 4.0–17% for wheat (a further decrease in yield of +0.1–1.8% from 2000), 9.5–15% for soybean (decrease of +0.7–1.0%), and 2.5–6.0% for maize (decrease of + 0.3–0.5%), with total losses worth $12–21 billion annually (an increase of +$1–3 billion in losses from 2000). Because our analysis uses crop data from the year 2000, which likely underestimates agricultural production in 2030 due to the need to feed a population increasing from approximately 6 to 8 billion people between 2000 and 2030, our calculations of crop production and economic losses are highly conservative. Our results suggest that O
3 pollution poses a growing threat to global food security even under an optimistic scenario of future ozone precursor emissions. Further efforts to reduce surface O
3 concentrations thus provide an excellent opportunity to increase global grain yields without the environmental degradation associated with additional fertilizer application or land cultivation.
► Surface O
3 will have an increasingly detrimental impact on future crop yields. ► Yields of wheat, soybean, and maize could be reduced by up to 26% globally in 2030. ► Global losses up to 17% are possible even in an optimistic scenario of future O
3. ► Agricultural losses worldwide may be worth $17–35 billion annually by 2030.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
We examine the potential global risk of increasing surface ozone (O₃) exposure to three key staple crops (soybean, maize, and wheat) in the near future (year 2030) according to two trajectories of O₃ ...pollution: the Intergovernmental Panel on Climate Change Special Report on Emissions Scenarios (IPCC SRES) A2 and B1 storylines, which represent upper- and lower-boundary projections, respectively, of most O₃ precursor emissions in 2030. We use simulated hourly O₃ concentrations from the Model for Ozone and Related Chemical Tracers version 2.4 (MOZART-2), satellite-derived datasets of agricultural production, and field-based concentration:response relationships to calculate crop yield reductions resulting from O₃ exposure. We then calculate the associated crop production losses and their economic value. We compare our results to the estimated impact of O₃ on global agriculture in the year 2000, which we assessed in our companion paper Avnery et al., 2011. In the A2 scenario we find global year 2030 yield loss of wheat due to O₃ exposure ranges from 5.4 to 26% (a further reduction in yield of +1.5–10% from year 2000 values), 15–19% for soybean (reduction of +0.9–11%), and 4.4–8.7% for maize (reduction of +2.1–3.2%) depending on the metric used, with total global agricultural losses worth $17–35 billion USD₂₀₀₀ annually (an increase of +$6–17 billion in losses from 2000). Under the B1 scenario, we project less severe but still substantial reductions in yields in 2030: 4.0–17% for wheat (a further decrease in yield of +0.1–1.8% from 2000), 9.5–15% for soybean (decrease of +0.7–1.0%), and 2.5–6.0% for maize (decrease of + 0.3–0.5%), with total losses worth $12–21 billion annually (an increase of +$1–3 billion in losses from 2000). Because our analysis uses crop data from the year 2000, which likely underestimates agricultural production in 2030 due to the need to feed a population increasing from approximately 6 to 8 billion people between 2000 and 2030, our calculations of crop production and economic losses are highly conservative. Our results suggest that O₃ pollution poses a growing threat to global food security even under an optimistic scenario of future ozone precursor emissions. Further efforts to reduce surface O₃ concentrations thus provide an excellent opportunity to increase global grain yields without the environmental degradation associated with additional fertilizer application or land cultivation.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Meeting the projected 50% increase in global grain demand by 2030 without further environmental degradation poses a major challenge for agricultural production. Because surface ozone (O3) has a ...significant negative impact on crop yields, one way to increase future production is to reduce O3‐induced agricultural losses. We present two strategies whereby O3 damage to crops may be reduced. We first examine the potential benefits of an O3 mitigation strategy motivated by climate change goals: gradual emission reductions of methane (CH4), an important greenhouse gas and tropospheric O3 precursor that has not yet been targeted for O3 pollution abatement. Our second strategy focuses on adapting crops to O3 exposure by selecting cultivars with demonstrated O3 resistance. We find that the CH4 reductions considered would increase global production of soybean, maize, and wheat by 23–102 Mt in 2030 – the equivalent of a ~2–8% increase in year 2000 production worth $3.5–15 billion worldwide (USD2000), increasing the cost effectiveness of this CH4 mitigation policy. Choosing crop varieties with O3 resistance (relative to median‐sensitivity cultivars) could improve global agricultural production in 2030 by over 140 Mt, the equivalent of a 12% increase in 2000 production worth ~$22 billion. Benefits are dominated by improvements for wheat in South Asia, where O3‐induced crop losses would otherwise be severe. Combining the two strategies generates benefits that are less than fully additive, given the nature of O3 effects on crops. Our results demonstrate the significant potential to sustainably improve global agricultural production by decreasing O3‐induced reductions in crop yields.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Pre-Columbian farmers of the Neotropical lowlands numbered an estimated 25 million by 1492, with at least 80 percent living within forest biomes. It is now well established that significant areas of ...Neotropical forests were cleared and burned to facilitate agricultural activities before the arrival of Europeans. Paleoecological and archaeological evidence shows that demographic pressure on forest resources-facilitated by anthropogenic burning-increased steadily throughout the Late Holocene, peaking when Europeans arrived in the late fifteenth century. The introduction of Old World diseases led to recurrent epidemics and resulted in an unprecedented population crash throughout the Neotropics. The rapid demographic collapse was mostly complete by 1650, by which time it is estimated that about 95 percent of all indigenous inhabitants of the region had perished. We review fire history records from throughout the Neotropical lowlands and report new high-resolution charcoal records and demographic estimates that together support the idea that the Neotropical lowlands went from being a net source of CO
2
to the atmosphere before Columbus to a net carbon sink for several centuries following the Columbian encounter. We argue that the regrowth of Neotropical forests following the Columbian encounter led to terrestrial biospheric carbon sequestration on the order of 2 to 5 Pg C, thereby contributing to the well-documented decrease in atmospheric CO
2
recorded in Antarctic ice cores from about 1500 through 1750, a trend previously attributed exclusively to decreases in solar irradiance and an increase in global volcanic activity. We conclude that the post-Columbian carbon sequestration event was a significant forcing mechanism of Little Ice Age cooling.
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BFBNIB, DOBA, INZLJ, IZUM, KILJ, NMLJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK, ZRSKP
Fire regimes in the lowland Neotropics are affected both by anthropogenic land use practices and natural climate variability. In Central America it is widely recognized that fire has been used as an ...agricultural tool for thousands of years, but the role of anthropogenic ignition as a determinant of past biomass burning frequency and magnitude has been debated. Little is known about the effects of short-term climate variability on fire regimes in this region of the world because of both the low temporal resolution of the available charcoal records and the obfuscating effects of anthropogenic burning throughout the late Holocene. Here we reconstruct 1400 years of fire history and environmental change on Ometepe Island, Lake Nicaragua, and perform statistical wavelet analysis on multiple proxy records to identify natural cycles of environmental variability possibly related to climate forcing. Our results indicate that extensive indigenous burning and landscape modification largely mask any climate signal in the paleo-fire record from AD 580 to 1400, with the exception of the period AD 775—1000 where high wavelet power exists at scales of 2—24 years. This time period coincides with a severe, two-century long regional drought that has been identified at other locations in Central America. High wavelet power at climate-relevant scales after ~AD 1400 in the Ometepe fire record suggests that periodic drought possibly caused by the El Niño Southern Oscillation and/or high-frequency solar cycles may have played a significant role in influencing the post-contact fire regime — a role that is largely concealed in the pre-European strata because of the overriding effects of anthropogenic burning.
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DOBA, IZUM, KILJ, NUK, OILJ, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Field studies demonstrate that exposure to elevated concentrations of surface ozone (O3) causes substantial reductions in the yields of many crops, yet O3 pollution is often overlooked as a ...potentially significant threat to current and future agricultural production. This study quantifies the global impact of O3 on crop yields in the present (year 2000) and near future (2030) under optimistic and pessimistic scenarios of O3 pollution, as well as associated crop production and economic losses for three key staple crops (soybean, maize, and wheat). This study additionally examines the potential of two strategies to reduce O3-induced yield losses that supplement controls on conventional O3 precursors: (1) O3 mitigation via gradual reductions of methane (CH4), an important greenhouse gas and a precursor to tropospheric background O 3 that to date has not been targeted for O3 abatement, and (2) adapting crops to elevated O3 by selecting cultivars with demonstrated O3 resistance relative to median-sensitivity varieties. Finally, this work contextualizes the estimated impact of O3 on global agricultural production with predicted climate change effects, and identifies regions of the world potentially at risk of reduced crop yields due to both O3 and climate change over the next few decades. Results indicate that present-day O3-induced global crop yield reductions are substantial, ranging from 4–15% for wheat, 9–14% for soybean, and 2–6% for maize worth $11–18 billion annually (USD2000). In the high O3 pollution scenario, year 2030 crop yield losses could be further reduced from 2000 levels by 2–10% for wheat, 1–11% for soybean, and 2-3% for maize, worth an additional $6–17 billion in losses globally. Controls on traditional O3 precursors in the optimistic pollution scenario appear to prevent extensive additional yield reductions in 2030, but total yield losses could remain significant, particularly for O3 sensitive crops (up to 15–17% for wheat and soybean). We find that the supplemental policy of CH4 control (via its additional O3 reductions) could considerably increase year 2030 production of soybean, maize and wheat by the equivalent of ∼2–8% from year 2000 levels, worth $3.5–15 billion worldwide. Choosing crop varieties with demonstrated O3 resistance relative to median sensitivity cultivars may improve year 2030 production of these crops by 12% from 2000 values, worth ∼$22 billion globally. This work suggests that the negative impact of O3 on agriculture now and in the near future could exceed predicted climate change effects for some crops (based on climate impact estimates available in the literature), and that regions at risk of yield reductions due to both O3 exposure and climate change include both significant agricultural producers (e.g. India, Russia, Brazil, and China) and net food importers (e.g. the Middle East) with possibly major implications for global food security. Efforts to reduce surface O3 concentrations and adapt crops to elevated O3 therefore provide an excellent opportunity to increase global agricultural production without the environmental damage associated with traditional agricultural intensification techniques or additional land cultivation.
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