Ecology, Climate Change and Related News

Conservation Science for a Healthy Planet

Category Archive: Drought

  1. Climate change and habitat conversion combine to homogenize nature- report on Costa Rican bird studies

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    • Land use change and drought favor the same species and threaten the same species so we may be losing biodiversity faster than we previously thought when we were studying these separately
    • Key strategies include protecting areas of wetter forests that expected to stay wet in the future; targetting conservation on wet-forest species that are particularly sensitive to habitat conversion and climate change; and incentivizing  landowners in wet regions to create or maintain patches of forests near or within their farms to better balance food production and biodiversity.

    August 18, 2017 University of California – Davis  Read full ScienceDaily article here

    Climate change and habitat conversion to agriculture are working together to homogenize nature, indicates a study in the journal Global Change Biology led by the University of California, Davis.

    In other words, the more things change, the more they are the same.

    While the individual impacts of climate change and habitat conversion on wildlife are well-recognized, little is known about how species respond to both stressors at once.

    In northwest Costa Rica, the study’s authors surveyed birds and plants at 120 sites that included rainforests, dry forests and farmland to determine how habitat conversion and climate-change-induced droughts affect tropical wildlife. They found that different bird species thrive in drier versus wetter areas of forests. In farmlands however, birds associated with dry sites were found everywhere, even in the wettest sites.


    Green-headed tanager (Tangara seledon). Credit: © Wilfred / Fotolia
    Across Central and South America, we are seeing large areas being converted from native forest to agriculture, and droughts are becoming more frequent,” said lead author Daniel Karp, an assistant professor in the UC Davis Department of Wildlife, Fish and Conservation Biology. “Both of these global pressures are favoring the same species and threatening the same species This means we may be losing biodiversity faster than we previously thought when we were studying climate change and habitat conversion individually.”
    most vulnerable birds at the study sites were those in the wet forests, which include tropical birds like tanagers, manakins, and woodcreepers. He noted that birds in the agricultural sites — such as blackbirds, doves, and sparrows — were more similar to those found in the dry forest, where there is less of a tree canopy and more grass cover….
    Daniel S. Karp, Luke O. Frishkoff, Alejandra Echeverri, Jim Zook, Pedro Juárez, Kai M. A. Chan. Agriculture erases climate-driven β-diversity in Neotropical bird communities. Global Change Biology, 2017; DOI: 10.1111/gcb.13821
  2. Incomplete ecological drought recovery new norm?

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    • If another drought arrives before trees and other plants have recovered from the last one, the ecosystem can reach a ‘tipping point’ where the plants’ ability to function normally is permanently affected.
    • A chronic state of incomplete drought recovery may be the new normal for the remainder of the 21st century and the risk of reaching “tipping points” that result in widespread tree deaths may be greater going forward,

    Aug 9 2017 see full ScienceDaily article here

    The amount of time it takes for an ecosystem to recover from a drought is an important measure of a drought’s severity. During the 20th century, the total area of land affected by drought increased, and longer recovery times became more common, according to new research published by Nature…

    …”If another drought arrives before trees and other plants have recovered from the last one, the ecosystem can reach a ‘tipping point’ where the plants’ ability to function normally is permanently affected,” Fang said.

    The team found that drought impacts increased over the 20th century. Given anticipated 21st century changes in temperature and projected increases in drought frequency and severity due to climate change, their findings suggest that recovery times will be slower in the future…

    Christopher R. Schwalm et al. Global patterns of drought recovery. Nature, 2017; 548 (7666): 202 DOI: 10.1038/nature23021

  3. Drought-affected trees die from water transport failure and carbon starvation

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    • As the number of hot droughts increases globally, scientists are looking to make more consistent predictions of what will happen to plants and vegetation in the future
    • The effect of tree death and die-off, as observed globally in recent decades, could affect the rate at which climate changes.

    Posted: 07 Aug 2017 08:15 AM PDT  read full article at Science Daily

    Drought-caused tree deaths are produced by a combination of hydraulic failure [cannot transport water from the roots to the leaves] and carbon starvation [closing pores in response to drought], shows new research. The finding, based on a meta-analysis by 62 scientists from across the world, will improve predictive models of how trees die in response to heat, drought, and other climate stresses...

    As the number of hot droughts increases globally, scientists are looking to make more consistent predictions of what will happen to plants and vegetation in the future.

    This matters for models used to predict climate change because plants take up a big portion of the carbon dioxide humans pump in the atmosphere. Therefore, the effect of tree death and die-off, as observed globally in recent decades, could affect the rate at which climate changes.

    …Trees respond to the stress of drought by closing those pores that let in carbon dioxide. At that point, they need to rely on their stored sugars and starches to stay alive, and could die from carbon starvation if they run out before the drought is over.

    On the other hand, if the tree loses too much water too quickly, an air bubble (embolism) will form and the tree has hydraulic failure, it cannot transport water from the roots to the leaves, which becomes lethal as the whole tree dries out…

    Adams et al. A multi-species synthesis of physiological mechanisms in drought-induced tree mortality. Nature Ecology & Evolution, 2017; DOI: 10.1038/s41559-017-0248-x

  4. Deforestation and climate change amplifying droughts in the Amazon

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    • Study finds human-driven changes in climate and land-use in Amazon’s 3rd “1-in-100 year” drought since 2005
    • man-made warming is accelerating the movement of water through the ecosystem, which can cause drought even if precipitation does not decrease. Warming also causes changes in the large-scale patterns of air motion (atmospheric circulation) that reduces rainfall in this region

    By John Abraham 3 August 2017 see full article in theGuardianUK

    If you are like me, you picture the Amazon region as an ever lush, wet, tropical region filled with numerous plant and animal species. Who would imagine the Amazon experiencing drought?……[there was a] very interesting paper recently published in Scientific Reports, entitled Unprecedented drought over tropical South America in 2016: significantly under-predicted by tropical SST[sea surface temperature]. So, what did this paper show?

    …the Amazon region does encounter periodic droughts. There was one in 2005, another in 2010, both of which were 100-year events, and the most recent one in 2015-2016.

    [The authors] quantified the precipitation deficits and water storage on the ground. They also used two different vegetation measures of drought. The results showed that the most recent drought was unprecedented in severity. ……

    …the authors found that the relationship between water temperatures and drought worked well for prior droughts (the 2005 and 2010 droughts as well as 1983 and 1998 droughts, also El Niño years) but fell apart in 2015-2016.

    …the predicted 2015-2016 drought should not have been nearly as severe or as large as it was. The paper also reports that the 2015-2016 drought clearly exceeded that of the 100-year events in 2005 and 2010. So, in approximately one decade, this zone has had three 100-year events. Quite astonishing…

    why was SST unable to explain the 2015-2016 drought, like it had for past events? Part of it has to do with land-use changes. That is, human changes to the land surface such as deforestation. Another part is related to warming from greenhouse gases…land-use changes can affect drought. As farmers deforest, for instance, they convert woodlands and forests into agricultural land. This changes not only the darkness (reflectivity) of the land, but it also impacts the transfer of water to and from the atmosphere (evapotranspiration). 

    how [does] warming affects droughts… As air temperatures increase, air is able to evaporate water more rapidly and dry out surfaces. At the same time, air can contain more water vapor so that when rain does occur, it is more often in heavy downpours. These two changes underlie what is referred to as an accelerated hydrological cycle. Simply put, man-made warming is accelerating the movement of water through the ecosystem, which can cause drought even if precipitation does not decrease. Warming also causes changes in the large-scale patterns of air motion (atmospheric circulation) that reduces rainfall in this region.

    Dr. Wang, who told me:

    Since oceanic forcing could not fully explain the severity of the latest drought, one will have to account for the roles of greenhouse gas warming, land use land cover changes, and/or dynamic ecosystem feedback in order to advance the understanding, attribution and prediction of extreme droughts in this region. The frequent recurrence of severe droughts in the recent decade may be a precursor of what the future might have in store for this regional climate and ecosystem.

    droughts in this part of the world create an increased risk for desertification and fire occurrence and hurt the region’s ecosystem, harm trees, and accelerate the release of carbon dioxide…

    A Erfanian et al. Unprecedented drought over tropical South America in 2016: significantly under-predicted by tropical SST. Sci Rep. 2017; 7: 5811. Published online 2017 Jul 19. doi:  10.1038/s41598-017-05373-2

     

  5. Atlantic/Pacific ocean temperature difference fuels drought and wildfires in CA and Southwest US; multi-year predictions possible

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    • New study shows that the large-scale difference between a warm Atlantic and relatively cold Pacific ocean temperatures plays a fundamental role in causing droughts, and enhancing wildfire risks in California and the southwest.
    • the Atlantic/Pacific temperature difference shows pronounced variations on timescales of more than 5 years. Like swings of a very slow pendulum, this implies that there is predictability in the large-scale atmosphere/ocean system, which we expect will have a substantial societal benefit.
    July 26, 2017 Institute for Basic Science Read full ScienceDaily article here
    A new study shows that difference in water temperature between the Pacific and the Atlantic oceans together with global warming impact the risk of drought and wildfire in southwestern North America.
    …”we were able to show that without anthropogenic effects, the droughts in the southwestern United States would have been less severe.”
    ..The new findings show that a warm Atlantic and a relatively cold Pacific enhance the risk for drought and wildfire in the southwestern US. “According to our study, the Atlantic/Pacific temperature difference shows pronounced variations on timescales of more than 5 years. Like swings of a very slow pendulum, this implies that there is predictability in the large-scale atmosphere/ocean system, which we expect will have a substantial societal benefit,”…
    …”we can use our climate computer model to determine whether on average the next year will have drier or wetter soils or more or less wildfires. Our yearly forecasts are far better than chance.”…

    Yoshimitsu Chikamoto, Axel Timmermann, Matthew J. Widlansky, Magdalena A. Balmaseda, Lowell Stott. Multi-year predictability of climate, drought, and wildfire in southwestern North America. Scientific Reports, 2017; 7 (1) DOI: 10.1038/s41598-017-06869-7

  6. Ocean temperature changes contributing to droughts

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    July 19, 2017 University of Exeter  see ScienceDaily article here

    Fluctuations in sea surface temperature are a factor in causing persistent droughts in North America and around the Mediterranean, new research suggests. A team from the universities of Exeter, Montpellier and Wageningen analysed data from 1957-2002 and found sea surface temperatures in the North Pacific and North Atlantic became increasingly variable, and extremes lasted for longer.

    Ocean temperatures are a major driver of conditions on land, and the researchers showed that the changes they observed correlated with increases in land temperature variability, and persistence of extreme temperatures. This in turn was associated with persistent droughts in North America and on land around the Mediterranean….

    “Our evidence shows that larger and more persistent variations in sea surface temperature have occurred in the North Atlantic and North Pacific and these contributed to more extreme and persistent temperature anomalies on parts of the world’s land surface,” said Professor Tim Lenton, of the University of Exete

    …”For instance, a long heatwave can have greater impacts on human mortality than the sum of individual hot days, and multi-year droughts can have greater agricultural economic impacts than the sum of individual dry years,” Professor Lenton said…

    Timothy M. Lenton, Vasilis Dakos, Sebastian Bathiany, Marten Scheffer. Observed trends in the magnitude and persistence of monthly temperature variability. Scientific Reports, 2017; 7 (1) DOI: 10.1038/s41598-017-06382-x

  7. Climate change to deplete water basins used for irrigation in US

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    Posted: 12 Jul 2017 08:04 AM PDT  read full ScienceDaily article here

    Certain hotspots in the country will experience severe reductions in crop yields by 2050, due to climate change’s impact on irrigation, a new study by climate scientists, economists, and agriculture experts finds. The most adversely affected region, according to the researchers, will be the Southwest. Already a water-stressed part of the country, this region is projected to experience reduced precipitation by midcentury. Less rainfall to the area will mean reduced runoff into water basins that feed irrigated fields.

    Production of cotton, the primary irrigated crop in the Southwest and in southern Arizona in particular, will drop to less than 10 percent of the crop yield under optimal irrigation conditions, the study projects. Similarly, maize grown in Utah, now only yielding 40 percent of the optimal expected yield, will decrease to 10 percent with further climate-driven water deficits.

    In the Northwest, water shortages to the Great Basin region will lead to large reductions in irrigated forage, such as hay, grasses, and other crops grown to feed livestock. In contrast, the researchers predict a decrease in water stress for irrigation in the southern Plains, which will lead to greater yields of irrigated sorghum and soybean.

    Elodie Blanc, Justin Caron, Charles Fant, Erwan Monier. Is Current Irrigation Sustainable in the United States? An Integrated Assessment of Climate Change Impact on Water Resources and Irrigated Crop Yields. Earth’s Future, 2017; DOI: 10.1002/2016EF000473

  8. Wastewater-To-Agriculture Project Is First Of Its Kind

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    Largest recycled water conveyance project in the country

    By Sara Jerome May 11, 2017 wateronline.com

    Water recycling for agricultural use is about to get a major boost through a massive reuse project in California that marks some first-evers.

    “Starting as early as December, [Modesto] will sell its highly treated wastewater to struggling nearby farmers. When it’s up and running, Modesto’s experiment should be California’s largest wastewater-to-agriculture reuse project, and it will mark the first time recycled water flows through a federal canal,” Grist recently reported.

    “The project will take tertiary-treated sewage from the cities of Modesto, Turlock and Ceres and route it through new pipelines into the Delta Mendota Canal, owned by the U.S. Bureau of Reclamation. From there, it will be purchased by Del Puerto Water District to irrigate crops on some 200 family farms along the west side of the San Joaquin Valley,” News Deeply explained.

    The project, known as the North Valley Regional Recycled Water Program, is the “single largest recycled water conveyance project in the country and the first water project for the U.S. Bureau of Reclamation, the owner and operator of the Delta-Mendota Canal,” the Turlock Journal reported. The effort will bring waste-to-farm techniques to some of the nation’s most productive farmland….

  9. U.S. Drought at Lowest Level in Nearly Two Decades

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    Andrea Thompson May 9th, 2017 full article here at climatecentral.org

    After years of intense, record-setting drought across the U.S., particularly in the Great Plains and California, the country is now experiencing its lowest level of drought in the 17 years since the U.S. Drought Monitor began its weekly updates.  Less than 5 percent of the U.S. was in some stage of drought as of May 4, the most recent update, compared to the 65 percent mired in drought in September 2012….

    afterDrought Has Disappeared from much of the U.S.  April 25, 2017 Credit: NASA Earth Observatory

    …The epicenters of drought were in the central and southern Plains states from 2011 to 2013 and California from 2012 to this winter. At the peak of its drought, more than half of California was experiencing “exceptional” drought conditions, the highest category. At the end of September 2011, more than 85 percent of Texas was in this category.

    Both droughts were fueled by a combination of dry weather and repeated, sizzling heat waves. The exceptional heat that blanketed much of the central and eastern portions of the country in 2012 boosted it to the hottest year on record for the U.S., while California experienced back-to-back record-hot years during its drought.

    That heat is probably the clearest link between climate change and droughts, as rising global temperatures fueled by increasing concentrations of greenhouse gases in the atmosphere tilt the odds in favor of record heat and away from record cold….

    Perhaps the clearest regional signals of climate change increasing drought are in the already arid Southwest, where droughts are expected to happen more often, last longer and be more intense than in the past. There is also some suggestion of more consecutive dry days for the Southern Plains, which could make it easier for that region to tip into drought…