Houston’s Flood Is a Design Problem

  • It’s not because the water comes in. It’s because it is forced to leave again.
  • Reducing impervious surfaces and improving water conveyance has a role to play
  • most important step is to reduce the velocity of water when it is channelized, so that it doesn’t deluge other sites. And then to stop moving water away from buildings and structures entirely, and to start finding new uses for it in place.
  • China’s “sponge cities” as a dramatic example—a government-funded effort to engineer new, permeable materials to anticipate and mitigate the flooding common to that nation….

Ian Bogost  The Atlantic  August 29 2017  Read full article here

…But the impact of flooding, particularly in densely developed areas like cities, is far more constant than a massive, natural disaster like Harvey exposes. The reason cities flood isn’t because the water comes in, not exactly. It’s because the pavement of civilization forces the water to get back out again.

Under normal circumstances, rain or snowfall soaks back into the earth after falling. It gets absorbed by grasslands, by parks, by residential lawns, by anywhere the soil is exposed. Two factors can impede that absorption. One is large quantities of rain in a short period of time. The ground becomes inundated, and the water spreads out in accordance with the topography. The second is covering over the ground so it cannot soak up water in the first place. And that’s exactly what cities do—they transform the land into developed civilization.

Roads, parking lots, sidewalks, and other pavements, along with asphalt, concrete, brick, stone, and other building materials, combine to create impervious surfaces that resist the natural absorption of water. In most of the United States, about 75 percent of its land area, less than 1 percent of the land is hardscape. In cities, up to 40 percent is impervious….

…In Houston’s case, catastrophic floods have been anticipated for some time. The combination of climate change, which produces more intense and unpredictable storms, and aggressive development made an event like this week’s almost inevitable. The Association of State Floodplain Managers has called for a national flood risk-management strategy, and the Houston Chronicle has called flood control the city’s “most pressing infrastructure need.” …

…Houston poses both a typical and an unusual situation for stormwater management. The city is enormous, stretching out over 600 square miles. It’s an epitome of the urban sprawl characterized by American exurbanism, where available land made development easy at the edges. Unlike New Orleans, Houston is well above sea level, so flooding risk from storm surge inundation is low. Instead, it’s rainfall that poses the biggest threat.

A series of slow-moving rivers, called bayous, provide natural drainage for the area. To account for the certainty of flooding, Houston has built drainage channels, sewers, outfalls, on- and off-road ditches, and detention ponds to hold or move water away from local areas. When they fill, the roadways provide overrun. The dramatic images from Houston that show wide, interstate freeways transformed into rivers look like the cause of the disaster, but they are also its solution, if not an ideal one. This is also why evacuating Houston, a metropolitan area of 6.5 million people, would have been a terrible idea. This is a city run by cars, and sending its residents to sit in gridlock on the thoroughfares and freeways designed to become rivers during flooding would have doomed them to death by water.

Accounting for a 100-year, 500-year, or “million-year” flood, as some are calling Harvey’s aftermath, is difficult and costly. Stiftel confirms that it’s almost impossible to design for these “maximal probable flood events,” as planners call them. Instead, the hope is to design communities such that when they flood, they can withstand the ill effects and support effective evacuations to keep people safe. “The Houston event seems like an illustration that we haven’t figured it out,” Stiftel says.

Many planners contend that impervious surface itself is the problem. The more of it there is, the less absorption takes place and the more runoff has to be managed. Reducing development, then, is one of the best ways to manage urban flooding. The problem is, urban development hasn’t slowed in the last half-century. Cities have only become more desirable, spreading outward over the plentiful land available in the United States….

….In other cases, floodplains have been managed through redevelopment that reduces impervious surfaces. Natural ground cover, permeable or semi-permeable pavers, and vegetation that supports the movement of water offer examples. These efforts dovetail with urban redevelopment efforts that privilege mixed-use and green space, associated with both new urbanism and gentrification. Recreation lands, conservation lands and easements, dry washes, and other approaches attempt to counterbalance pavement when possible. Stiftel cites China’s “sponge cities” as a dramatic example—a government-funded effort to engineer new, permeable materials to anticipate and mitigate the flooding common to that nation….

….Reducing impervious surface and improving water conveyance has a role to play, but the most important step in sparing cities from flooding is to reduce the velocity of water when it is channelized, so that it doesn’t deluge other sites. And then to stop moving water away from buildings and structures entirely, and to start finding new uses for it in place.

That can be done by collecting water into cisterns for processing and reuse—in some cases, Debo explains, the result can even save money by reducing the need to rely on utility-provided water. Adding vegetation, reclaiming stormwater, and building local conveyance systems for delivery of this water offer more promising solutions….

….Instead of looking for holistic answers, site-specific ones must be pursued instead. Rather than putting a straight channel through a subdivision, for example, Debo suggests designing one to meander through it, to decrease the velocity of the water as it exits

…But there are some regions that just shouldn’t become cities. “Parts of Houston in the floodway, parts of New Orleans submerged during Katrina, parts of Florida—these places never should have been developed in the first place,” Debo concludes. Add sea-level rise and climate-change superstorms, and something has to give.

…Residential homeowners who install a new cement patio or driveway might not even realize that they are channeling water down-grade to their neighbors, or overwhelming a local storm drain. Citizens can also influence stormwater issues within their municipalities. Many folks know that they have a local city council and school board, but local planning, zoning, and urban design agencies also hold regular public meetings—unfortunately, most people only participate in this aspect of local governance when they have an axe to grind. For the average American concerned with the deluge, the best answer is to replace an occasional, morbid curiosity with flooding with a more sophisticated, long-term interest in stormwater management.

Did Climate Change Intensify Harvey? Yes- amplifying worst effects

Robinson Meyer  read full article in The Atlantic

Every so often, the worst-case scenario comes to pass.  As of Sunday afternoon, the remnants of Hurricane Harvey seem likely to exceed the worst forecasts that preceded the storm. The entire Houston metropolitan region is flooding: Interstates are under feet of water, local authorities have asked boat owners to join rescue efforts, and most of the streams and rivers near the city are in flood stage….“Local rainfall amounts of 50 inches would exceed any previous Texas rainfall record. The breadth and intensity of this rainfall are beyond anything experienced before,” said a statement from the National Weather Service. “Catastrophic flooding is now underway and expected to continue for several days. ”…
This means that thousands of people—and perhaps tens of thousands of people—are facing a terrifying and all-too-real struggle to survive right now. In an age when the climate is changing rapidly, a natural question to ask is: What role did human-caused global warming play in strengthening this storm?Climate scientists, who specialize in thinking about the Earth system as a whole, are often reticent to link any one weather event to global climate change. But they say that aspects of the case of Hurricane Harvey—and the recent history of tropical cyclones worldwide—suggest global warming is making a bad situation worse.…Climate change is caused by the release of greenhouse gases like carbon dioxide and methane into the atmosphere. These gases prevent some of the sun’s rays from bouncing back into space, trapping heat in the planetary system and raising air temperatures all over the world….

Storms like Harvey are helped by one of the consequences of climate change: As the air warms, some of that heat is absorbed by the ocean, which in turn raises the temperature of the sea’s upper layers.
Harvey benefitted from unusually toasty waters in the Gulf of Mexico. As the storm roared toward Houston last week, sea-surface waters near Texas rose to between 2.7 and 7.2 degrees Fahrenheit above average. These waters were some of the hottest spots of ocean surface in the world. The tropical storm, feeding off this unusual warmth, was able to progress from a tropical depression to a category-four hurricane in roughly 48 hours.“This is the main fuel for the storm,” says Kevin Trenberth, a senior scientist at the U.S. National Center for Atmospheric Research. “Although these storms occur naturally, the storm is apt to be more intense, maybe a bit bigger, longer-lasting, and with much heavier rainfalls [because of that ocean heat].”……the hurricane churned up water 100 or even 200 meters below the surface, said Trenberth, but this water was still warm—meaning that the storm could keep growing and strengthening. “Harvey was not in a good position to intensify the way it did, because it was so close to land. It’s amazing it was able to do that,” he told me…

…Trenberth says that the extra heat could make the storm more costly and more powerful, overpowering and eventually breaking local drainage systems.

The human contribution can be up to 30 percent or so up to the total rainfall coming out of the storm,” he said. “It may have been a strong storm, and it may have caused a lot of problems anyway—but [human-caused climate change] amplifies the damage considerably.”…

  • How Harvey went from a little-noticed storm to a behemoth

By Sandhya Somashekhar August 27 at 6:06 PM read full Washington Post article

Even if Harvey had been a milder storm, spinning lazily across the Gulf of Mexico, there would have been reasons for alarm early last week. For starters, the jet stream — the air current that meanders across the continent, pushing storms along a familiar path — flowed far north of Texas, and thus when Harvey crashed into the state there was nothing in the atmosphere to shove it somewhere else. Harvey stalled.

…Harvey also proved that the Gulf of Mexico — in late August, in a warming climate — can prove explosive for the development of what is generically called a tropical cyclone. In barely more than a day the storm went from a disorganized tropical depression to a significant hurricane and then all the way up to Category 4 — the second-highest rating on the Saffir-Simpson hurricane intensity scale, which is based on wind speed.

The result: a record-setting storm that within 24 hours plunged much of the nation’s fourth-largest city and its surroundings under feet of choppy brown water. It threatens to submerge even more of the region during the next few days.

“There are a lot of worst-case-scenario stars that aligned,” said Marshall Shepherd, a professor of atmospheric sciences at the University of Georgia and a past president of the American Meteorological Society. “As bad as it is now, we still have days of this to go.”

….A stunning amount of rain has fallen over Texas so far, and it is expected to continue for several more days as the storm creeps along, weakening slightly. In general, things will probably get worse before they get better; some areas might see as many as 50 inches of rainfall when all is said and done, wreaking damage that experts predict could lead to years of recovery across the region.

As of Sunday afternoon, the storm had deposited 9 trillion gallons over Southeast Texas, as bands of rain picked up moisture from the Gulf. That’s enough water to fill up the Great Salt Lake twice over, meteorology student Matthew Cappucci wrote for The Washington Post….

Experts say the lack of “steering currents” to move the storm along is unusual and probably responsible for the scale of the flooding. As of Sunday evening, the center of the storm was virtually parked at a spot about 25 miles northwest of the coastal town of Victoria — crawling southeast at 2 miles per hour toward the Gulf.

With a more common tropical storm, the damage in any one place would be mitigated by the fact that the storms move quickly, spreading the rain over a larger area.

Perhaps making things worse is something called the “brown ocean effect,” which hypothesizes that storms, which typically get their energy over the ocean or another large body of water, can absorb that energy and moisture from rain-soaked land. “The land, in effect, mimics the energy supply of the ocean,” University of Maryland Baltimore County professor Jeff Halverson wrote for the Capital Weather Gang….

Related: What you can and can’t say about climate change and Hurricane Harvey

A Galápagos seabird’s population expected to shrink with ocean warming

 

Posted: 25 Aug 2017 08:28 AM PDT  Read full ScienceDaily article here

Within the next century, rising ocean temperatures around the Galápagos Islands are expected to make the water too warm for a key prey species, sardines, to tolerate. A new study uses decades of data on the diet and breeding of a tropical seabird, the Nazca booby, to understand how the future absence of sardines may affect the booby population.

Interior secretary recommends Trump alter at least three national monuments, including Bears Ears

  • Zinke proposed reducing the size of Bears Ears and Grand Staircase-Escalante national monuments, both in Utah, and Cascade-Siskiyou National Monument in Oregon
  • in addition to radically shrinking Bears Ears and perhaps other sites, he is pushing to allow activities at some monuments that previous presidents restricted or barred outright
  • no president had ever sought the kind of rollbacks Trump is contemplating.

By Juliet Eilperin and Darryl Fears August 24 Read full Washington Post article here

Interior Secretary Ryan Zinke recommended Thursday that President Trump alter at least three dramatic national monuments and change the way others are managed, moves that would represent the greatest reversal of protections for such sites in more than a century.

Zinke proposed reducing the size of Bears Ears and Grand Staircase-Escalante national monuments, both in Utah, and Cascade-Siskiyou National Monument in Oregon, according to multiple individuals briefed on the decision. Together, the Utah sites span more than 3.2 million acres.

Zinke’s report, which the White House did not release, launches what will be a legal and political battle over a relatively obscure law that grants a president wide latitude in preserving federal lands and waters that are threatened.

After spending nearly four months examining more than two dozen monuments established by Bill Clinton, George W. Bush and Barack Obama under the 1906 Antiquities Act, Zinke is calling for less major change than some conservatives advocated. But in addition to radically shrinking Bears Ears and perhaps other sites, he is pushing to allow activities at some monuments that previous presidents restricted or barred outright.

“The recommendations I sent to the president on national monuments will maintain federal ownership of all federal land and protect the land under federal environmental regulations,” Zinke said in a statement, “and also provide a much needed change for the local communities who border and rely on these lands for hunting and fishing, economic development, traditional uses, and recreation.”

….In his statement, Zinke described his proposal as a reasonable remedy to years of presidents’ unilaterally exercising their authority without giving adequate consideration to the people living closest to these public lands.

…Yet John Leshy, who served as Interior’s solicitor in the Clinton administration and is now a professor at the University of California’s Hastings College of Law, noted that no president had ever sought the kind of rollbacks Trump is contemplating.  “The scale of this, and the sweep of this, is definitely unprecedented,” Leshy said.

Ethan Lane, executive director of the public lands council at the National Cattlemen’s Beef Association, said the administration’s push reflected that “they’re concerned with rural America.” “They’ve been talking to groups that feel like maybe they weren’t included in the process,” Lane said. “Ranchers across the West are certainly part of that.”

The Interior Department gave no specifics of Zinke’s recommendations, instead releasing a report summary that described each of the 27 protected areas scrutinized as “unique.” Even so, his proposal takes direct aim at several, according to several individuals who asked for anonymity because the report has yet to be made public….

Texas in direct path of intensifying, ‘astounding’ Hurricane Harvey; Gulf waters warmer than normal; rainfall may equal annual total, shattering records

  • When it comes ashore, forecasters said, it could have sustained winds of 125 miles per hour, with a 12-foot storm surge.
  • it is projected to stall on the Texas coast for several days, which could dump historic quantities of rain, with some places seeing as much as 35 inches, the hurricane center said.
  • In just a few days, the storm may dispense the amount of rain that normally falls over an entire year, shattering records.

August 24 2017 see full Washington Post article here

Texas is bracing for potentially catastrophic flooding and winds as Hurricane Harvey intensified Thursday and cruised toward a late Friday impact near Corpus Christi.

The National Hurricane Center described Harvey’s sudden strengthening as “astounding.” The storm is expected to strike as a Category 3 hurricane — meaning with winds greater than 111 miles per hour — making it the most powerful storm to make landfall in the United States since Hurricane Wilma in 2005.

…Harvey would be the first hurricane to hit Texas since Ike, a high Category 2 storm, came ashore in September 2008 in Galveston and caused tens of billions of dollars in property damage.

Hurricane Harvey is seen in the Texas Gulf Coast on August 24, 2017. (NOAA/Reuters)

…The Gulf of Mexico is vitally important for the nation’s oil infrastructure. Offshore platforms produce about 1.7 million barrels a day, nearly a fifth of U.S. crude oil production. More than 45 percent of U.S. petroleum refining capacity lies along the Gulf Coast as well as 51 percent of total U.S. natural gas processing plant capacity, according to Energy Department data

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Harvey forecast to slam Texas coast as major hurricane with ‘devastating’ flooding

By Brian McNoldy and Jason Samenow August 25 at 10:10 AM Washington Post

…Not only are the rain and flooding concerns huge, but the storm also has the potential to generate destructive winds and a devastating storm surge — or raise the water as much as 6 to 12 feet above normally dry land at the coast.

…An incredible amount of rain, 15 to 25 inches with isolated amounts of up to 35 inches, is predicted along the middle and upper Texas coast, because the storm is expected to stall and unload torrents for four to six straight days. The National Hurricane Center said it expects “devastating and life-threatening” flash flooding. In just a few days, the storm may dispense the amount of rain that normally falls over an entire year, shattering records.

…The National Weather Service office in Corpus Christi, near where the storm is expected to make landfall, said that due to the combination of flooding from storm surge and rainfall, “locations may be uninhabitable for an extended period.” It warned of “structural damage to buildings, with many washing away” and that “streets and parking lots become rivers of raging water with underpasses submerged.”…

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Here’s Why Hurricane Harvey Is So Scary and Unprecedented

Emily Atkin New Republic

….According to Texas State Climatologist John Nielsen-Gammon, hurricanes usually come with only one of two awful characteristics—either heavy, persistent rainfall or strong, violent winds and storm surge. It looks like Hurricane Harvey could have both, because unique wind patterns may prevent the storm from moving quickly out of the region….

….“Climate change is definitely impacting the maximum intensity of rainfall,” Nielsen-Gammon told me, explaining how the warmer atmosphere is able to hold more moisture and therefore release more rainfall during storms….

A Texas-size flood threatens the Gulf Coast, and we’re so not ready

Dynamic conservation for migratory waterbirds – new publication co-authored by TNC, Cornell, Point Blue

Coauthored by scientists from: The Nature Conservancy of California, Cornell Lab of Ornithology, Point Blue Conservation Science (Matt Reiter, Sam Veloz, Catherine Hickey and Nathan Elliott) and University of Melbourne.

Abstract: In an era of unprecedented and rapid global change, dynamic conservation strategies that tailor the delivery of habitat to when and where it is most needed can be critical for the persistence of species, especially those with diverse and dispersed habitat requirements. We demonstrate the effectiveness of such a strategy for migratory waterbirds.

We analyzed citizen science and satellite data to develop predictive models of bird populations and the availability of wetlands, which we used to determine temporal and spatial gaps in habitat during a vital stage of the annual migration. We then filled those gaps using a reverse auction marketplace to incent qualifying landowners to create temporary wetlands on their properties. This approach is a cost-effective way of adaptively meeting habitat needs for migratory species, optimizes conservation outcomes relative to investment, and can be applied broadly to other conservation challenges.

Urban land transformation and electricity production impact river ecosystems on much larger scale

  • The results indicate that urban land transformation and electricity production together affect seven percent of U.S. streams, which influence habitats for more than 60 percent of all North American freshwater fish, mussel, and crayfish species.

August 23, 20 DOE/Oak Ridge National Laboratory  Read full ScienceDaily article here

New mapping methods can help urban planners minimize the environmental impacts of cities’ water and energy demands on surrounding stream ecologies.

Using streamflow data from the U.S. Geological Survey, the researchers mapped changes to natural hydrology to assess how infrastructure development and competition over water resources affects the environment at a national scale.

The results indicate that urban land transformation and electricity production together affect seven percent of U.S. streams, which influence habitats for more than 60 percent of all North American freshwater fish, mussel, and crayfish species.

…In the five cities, urban land transformations negatively affected more stream length overall than any other factor considered, including electricity production. The introduction of roads, buildings, and other impervious surfaces alters the natural water cycle, displaces water supplies for downstream communities and can threaten the loss of rich and diverse aquatic species.

…”Both the source and solution to global environmental challenges may lie in the hands of cities. Unfortunately, the changes we discuss are highly transformative, not cheap,” McManamay said. “Our goal here is to give cities a way to look at the big picture, so to speak, and to generate metrics that will help them move toward more environmentally sound policies as they continue to develop.

Ryan A. McManamay et al. US cities can manage national hydrology and biodiversity using local infrastructure policy. Proceedings of the National Academy of Sciences, 2017; 201706201 DOI: 10.1073/pnas.1706201114

Worldwide 100% renewable energy needed and possible by 2050, per new publication

  • A detailed roadmap for 139 countries outlines a path to a future powered entirely by wind, water and solar energy.

  • Such a transition could mean less worldwide energy consumption due to the efficiency of clean, renewable electricity; a net increase of over 24 million long-term jobs; an annual decrease in 4-7 million air pollution deaths per year; stabilization of energy prices; and annual savings of over $20 trillion in health and climate costs

August 24, 2017  read full Cosmos article here and ScienceDaily article here

Everybody wants to change the world. Few of us publish research detailing exactly how to do it.

Stanford’s Mark Z. Jacobson, who led a 2015 effort to create a state-by-state plan for a US transition to 100% renewable energy, has published similar research on a much larger scale, examining scenarios in which 139 countries could be powered purely by wind, water and solar (WWS) by the year 2050.

In scope and scale, the paper – published in the new energy journal Joule – is a significant expansion on Jacobson’s prior work. It isn’t limited to each country’s electricity sector – it examines the electrification and decarbonisation of transportation, heating, cooling, industry, agriculture, forestry and fishing. The authors chose the 139 countries, which between them cover 99% of the world’s carbon emissions, because the necessary energy data about them were available through the International Energy Agency (IEA).

The latest roadmap to a 100% renewable energy future from Stanford’s Mark Z. Jacobson and 26 colleagues is the most specific global vision yet, outlining infrastructure changes that 139 countries can make to be entirely powered by wind, water, and sunlight by 2050 after electrification of all energy sectors. Such a transition could mean less worldwide energy consumption due to the efficiency of clean, renewable electricity; a net increase of over 24 million long-term jobs; an annual decrease in 4-7 million air pollution deaths per year; stabilization of energy prices; and annual savings of over $20 trillion in health and climate costs….

….“Both individuals and governments can lead this change. Policymakers don’t usually want to commit to doing something unless there is some reasonable science that can show it is possible, and that is what we are trying to do,” says Jacobson. “We are not saying that there is only one way we can do this, but having a scenario gives people direction.”

His ideal policy outcome would see “governments in many countries of the world commit to 100% clean, renewable energy in all sectors by 2050 with 80% by 2030”.

“To avoid 1.5 C global warming, we need 80% reduction of everything by 2030 and 100% by 2050. We think a faster acceleration is possible at reasonable to low cost.”

….Jacobson’s paper is designed to serve as a vision for future, but even Finkel’s proposal [a recent review authored by Australia’s chief scientist Alan Finkel] for a far less ambitious emissions reduction target has not been adopted several months after it was proposed….

Assessing ExxonMobil’s climate change communications (1977–2014)

  • 83% of peer-reviewed papers and 80% of internal documents acknowledge that climate change is real and human-caused, yet only 12% of advertorials do so, with 81% instead expressing doubt.
  • ExxonMobil contributed to advancing climate science—by way of its scientists’ academic publications—but promoted doubt about it in advertorials

Geoffrey Supran1 and Naomi Oreskes. Assessing ExxonMobil’s climate change communications (1977–2014). Published 23 August 2017 Environmental Research Letters, Volume 12, Number 8

ABSTRACT: This paper assesses whether ExxonMobil Corporation has in the past misled the general public about climate change. We present an empirical document-by-document textual content analysis and comparison of 187 climate change communications from ExxonMobil, including peer-reviewed and non-peer-reviewed publications, internal company documents, and paid, editorial-style advertisements (‘advertorials’) in The New York Times. We examine whether these communications sent consistent messages about the state of climate science and its implications—specifically, we compare their positions on climate change as real, human-caused, serious, and solvable. In all four cases, we find that as documents become more publicly accessible, they increasingly communicate doubt. This discrepancy is most pronounced between advertorials and all other documents. For example, accounting for expressions of reasonable doubt, 83% of peer-reviewed papers and 80% of internal documents acknowledge that climate change is real and human-caused, yet only 12% of advertorials do so, with 81% instead expressing doubt. We conclude that ExxonMobil contributed to advancing climate science—by way of its scientists’ academic publications—but promoted doubt about it in advertorials. Given this discrepancy, we conclude that ExxonMobil misled the public. Our content analysis also examines ExxonMobil’s discussion of the risks of stranded fossil fuel assets. We find the topic discussed and sometimes quantified in 24 documents of various types, but absent from advertorials. Finally, based on the available documents, we outline ExxonMobil’s strategic approach to climate change research and communication, which helps to contextualize our findings.

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Read related InsideClimateNews article here

A comprehensive, peer-reviewed academic study of ExxonMobil’s internal deliberations, scientific research and public rhetoric over the decades has confirmed empirically that the oil giant misled the public about what it knew about climate change and the risks posed by fossil fuel emissions, the authors said on Tuesday.

The paper confirms the findings of a 2015 investigative series by InsideClimate News that was based largely on the company’s internal records, and also of independent work published by the Los Angeles Times. That reporting ignited investigations by state attorneys general that are still in litigation….

Warmer waters from climate change will leave fish shrinking, gasping for air

  • Fish are expected to shrink in size by 20 to 30 per cent if ocean temperatures continue to climb due to climate change

August 21, 2017 University of British Columbia read full ScienceDaily article here

…A new study by researchers at the University of British Columbia provides a deeper explanation of why fish are expected to decline in size. “Fish, as cold-blooded animals, cannot regulate their own body temperatures. When their waters get warmer, their metabolism accelerates and they need more oxygen to sustain their body functions….There is a point where the gills cannot supply enough oxygen for a larger body, so the fish just stops growing larger.”…

….as fish like cod increases its weight by 100 per cent, its gills only grow by 80 per cent or less. When understood in the context of climate change, this biological rule reinforces the prediction that fish will shrink and will be even smaller than thought in previous studies.

Warmer waters increase fish’s need for oxygen but climate change will result in less oxygen in the oceans. This means that gills have less oxygen to supply to a body that already grows faster than them. The researchers say this forces fish to stop growing at a smaller size to be able to fulfill their needs with the little oxygen available to them.

Some species may be more affected by this combination of factors. Tuna, which are fast moving and require more energy and oxygen, may shrink even more when temperatures increase. Smaller fish will have an impact on fisheries production as well as the interaction between organisms in the ecosystems.

Daniel Pauly, William W. L. Cheung. Sound physiological knowledge and principles in modeling shrinking of fishes under climate change. Global Change Biology, 2017; DOI: 10.1111/gcb.13831