All posts by Garry Peterson

Prof. of Environmental science at Stockholm Resilience Centre at Stockholm University in Sweden.
Ecological Management, New Orleans

Dams limit wetland restoration in Mississippi Delta

1 Comment

Cornelia Dean in the New York Times writes Dams Are Thwarting Louisiana Marsh Restoration, Study Says. She describes recent research by Michael Blum and Harry Roberts Drowning of the Mississippi Delta due to insufficient sediment supply and global sea-level rise (doi:10.1038/ngeo553) that estimates that dams have reduced sediment outflows by 50% reducing the potential for New Orleans wetland restoration:

Desperate to halt the erosion of Louisiana’s coast, officials there are talking about breaking Mississippi River levees south of New Orleans to restore the nourishing flow of muddy water into the state’s marshes.

But in a new analysis, scientists at Louisiana State University say inland dams trap so much sediment that the river no longer carries enough to halt marsh loss, especially now that global warming is speeding a rise in sea levels.

As a result, the loss of thousands of additional square miles of marshland is “inevitable,” the scientists report in Monday’s issue of Nature Geoscience.

The finding does not suggest it would be pointless to divert the muddy water into the marshes, one of the researchers, Harry H. Roberts, said in an interview. “Any meaningful restoration of our coast has to involve river sediment,” said Dr. Roberts, a coastal scientist.

But he said officials would have to choose which parts of the landscape could be saved and which must be abandoned, and to acknowledge that lives and businesses would be disrupted. Instead of breaking levees far south of New Orleans, where relatively few people live, Dr. Roberts said, officials should consider diversions much closer to New Orleans, possibly into the LaFourche, Terrebonne or St. Bernard basins.

“It’s going to be an excruciating process to decide where that occurs,” Dr. Roberts said of the levee-breaking.

Sediment carried by the Mississippi built up the marshes of Louisiana over thousands of years, but today inland dams trap at least half of it, Dr. Roberts said. He pointed out that there were 8,000 dams in the drainage basin of the Mississippi.

In their article Blum and Roberts conclude that significant sea level rise is inevitable even if sediment loads are restored, because sea level is now rising at least three times faster than the building of the Mississippi delta.

General

Paul Krugman on Betraying the Planet

2 Comments

In his New York Times column economist Paul Krugman strongly criticizes climate change denial in the US congress:

…we’re facing a clear and present danger to our way of life, perhaps even to civilization itself. How can anyone justify failing to act?

Well, sometimes even the most authoritative analyses get things wrong. And if dissenting opinion-makers and politicians based their dissent on hard work and hard thinking — if they had carefully studied the issue, consulted with experts and concluded that the overwhelming scientific consensus was misguided — they could at least claim to be acting responsibly.

But if you watched the debate on Friday, you didn’t see people who’ve thought hard about a crucial issue, and are trying to do the right thing. What you saw, instead, were people who show no sign of being interested in the truth. They don’t like the political and policy implications of climate change, so they’ve decided not to believe in it — and they’ll grab any argument, no matter how disreputable, that feeds their denial.

Indeed, if there was a defining moment in Friday’s debate, it was the declaration by Representative Paul Broun of Georgia that climate change is nothing but a “hoax” that has been “perpetrated out of the scientific community.” I’d call this a crazy conspiracy theory, but doing so would actually be unfair to crazy conspiracy theorists. After all, to believe that global warming is a hoax you have to believe in a vast cabal consisting of thousands of scientists — a cabal so powerful that it has managed to create false records on everything from global temperatures to Arctic sea ice.

Yet Mr. Broun’s declaration was met with applause.

Given this contempt for hard science, I’m almost reluctant to mention the deniers’ dishonesty on matters economic. But in addition to rejecting climate science, the opponents of the climate bill made a point of misrepresenting the results of studies of the bill’s economic impact, which all suggest that the cost will be relatively low.

Still, is it fair to call climate denial a form of treason? Isn’t it politics as usual?

Yes, it is — and that’s why it’s unforgivable.

Do you remember the days when Bush administration officials claimed that terrorism posed an “existential threat” to America, a threat in whose face normal rules no longer applied? That was hyperbole — but the existential threat from climate change is all too real.

Yet the deniers are choosing, willfully, to ignore that threat, placing future generations of Americans in grave danger, simply because it’s in their political interest to pretend that there’s nothing to worry about. If that’s not betrayal, I don’t know what is.

Visualization

Vienna Zoo: Wildlife and Humanity

Leave a comment

(Photo by Christoph Steinbrener and Rainer Dempf.)

Sculptor Christoph Steinbrener and photographer Reiner Dempf have modified the animal enclosures of the Vienaa Zoo for summer 2009 (June 10 – October 18) for their show Trouble in Paradise. Their show transforms the idealized wild setting in which animals into settings that contain some our activities that are endangering animal populations outside of zoos.

The artists describe their show as:

… A sunken car wreck at the rhinos, railroad tracks in the bison pen or toxic waste in the aquarium are unexpectedly interfering with our notions of idyllic wildlife. The viewer is forced to reconsider traditional modes of animal presentation and simultaneously to question the authenticity of concepts which are restaging ‘natural’ environments while they are increasingly endangered.

…Present-day conceptions of zoological gardens aim at the presentation of animals in an idyllic and apparently natural environment, untouched by civilization. But this is a contemporary conception, since courtly menageries and kennels were adapted to the exposure of animals as decorative objects. Until the early years of the 20th century, animals were part of a preferably spectacular and exotic staging, to the entertainment and amazement of the public. The artificial and the sensational were foregrounded, without creating a realistic setting of the natural environment of the animals.

(Photo by Christoph Steinbrener and Rainer Dempf.)

(Photo by Christoph Steinbrener and Rainer Dempf.)

(Photo by Christoph Steinbrener and Rainer Dempf.)

All photos by Christoph Steinbrener and Rainer Dempf from their webpage.

via Pruned.

Ecological Economics, Ecosystem services

Michael Pollan interviewed in Vancouver’s the Tyee

Leave a comment

Systems thinking food writer Michael Pollan interviewed by Vancouver’s the Tyee after a talk in support of the University of British Columbia’s Farm. The interview – Garden Fresh – discusses US agricultural policy and resilience food systems:

On whether he’s trying to rally a movement in time to avert disaster, or just prepare us for the inevitable mess caused by scarcer oil, degrading ecologies, and global warming:

“It’s more the latter. We need to have these alternatives around and available when the shit hits the fan, basically.

“One of the reasons we need to nurture several different ways of feeding ourselves — local, organic, pasture-based meats, and so on – is that we don’t know what we’re going to need and we don’t know what is going to work. To the extent that we diversify the food economy, we will be that much more resilient. Because there will be shocks. We know that. We saw that last summer with the shock of high oil prices. There will be other shocks. We may have the shock of the collapsing honey bee population. We may have the shock of epidemic diseases coming off of feed lots. We’re going to need alternatives around.

“When we say the food system is unsustainable we mean that there is something about it, an internal contradiction, that means it can’t go on the way it is without it breaking up. And I firmly believe there will be a breakdown.”

General

What is resilience thinking and what is it not

2 Comments

Adaptive cycleVictor Galaz‘s post Machine Fetishism, Money and Resilience Theory reflected on Alf Hornborg‘s recent paper Zero-Sum World: Challenges in Conceptualizing Environmental Load Displacement and Ecologically Unequal Exchange in the World-System, in which, among other things, Hornborg presents a partial critique of what he calls “the gospel of resilence” – resilience theory and adaptive management.

There have been many comments on Victor’s post, including responses from the paper’s author.  To highlight this discussion, I’ve hoisted some points from the comments on that post.

Alf Hornborg writes that he is waiting for a convincing response to his criticism of social-ecological resilience:

At the most general level, the rhetoric on social-ecological resilience is framed in terms of a nomothetic search for the functional principles of socio-ecological systems (SES), as if human ecology was analogous to medicine.  SES are approached like biological systems with processes of adaptation and change that can be studied from a detached, objective position. The recurrent aim is to increase our “understanding” of how SES actually function, as if more data and better models could improve our management of these systems (again, analogous to medical practice).

Rather than try to develop a conspicuously and naively non-political cybernetic etiology of socio-ecological degradation – based on the assumption that such processes, irrespective of capitalist extractivism, are universally patterned, predictable, and potentially manageable – I challenge resilience theorists to address the operation of the global economic system that is the very obvious source of such processes. The attempt to provide an abstract vocabulary for describing SES often cries out for empirical examples that might get the discussion grounded in the real politics of human-environmental relations. For example, when it is argued that we must define on which scales agency is located and how an increase or decrease of scope for agency at one level influences agency on other levels, we need to consider a concrete case in order to assess whether the concept of resilience is really the most useful way of accounting for what actually seems to be a (rather well understood) problem of power.

Is “path dependence” so much better than various understandings of cultural, social, political, and generally structural problems of inertia and conservatism?

What do we gain by rephrasing environmental conflict and armed resistance as “regulation”?

How can we hope to predict and manage the abrupt surprises and discontinuities implied by notions of “critical thresholds” and “flipping”?

Why should concepts such as “non-linear dynamics”, “disturbance”, “opportunities for innovation”, “adaptation”, and “renewal” provide a better way of understanding what Joseph Tainter and many others for decades have recognized as socio-ecological collapse?

What are, quite frankly, the discursive/ideological benefits of subsuming social systems within the vocabulary of natural science?

I find it hard to respond to this critique because I do not recognize my work or that of my colleagues in the Resilience Alliance in Hornborg’s characterization of resilience thinking.

Perhaps this is because his article only shallowly engages the resilience literature, focusing on the Linking book edited by Berkes and Folke (an overview of resilience books and articles is available on the Resilience Alliance website), but I think it may be because Resilience thinking is not a formula for explaining how the world works.  In a recent paper, Steve Carpenter and Buz Brock described resilience as:

Resilience is a broad, multifaceted, and loosely organized cluster of concepts, each one related to some aspect of the interplay of transformation and persistence. Thus, resilience does not come down to a single testable theory or hypothesis. Instead it is a changing constellation of ideas, some of which are testable through the usual practices of natural or social science. Although particular ideas may be rejected or supported, the program of research on resilience itself is evaluated in a different way. As long as resilience thinking produces interesting research ideas, people are likely to pursue it. When it seems empty of ideas, it will be abandoned or transformed into something else.

Below I give some specific response to some aspects of Homborg’s comments:

  • Neither ecosystems nor society are super-organisms – and therefore most resilience researchers do not think that medicine or health are good metaphors for managing, manipulating, or understanding ecosystems.
  • Social-ecological systems are different from ecosystems or social systems.  How they are different was specifically addressed in the 2002 book Panarchy in a chapter by Westley F, Carpenter SR, Brock WA,. Holling CS, and Gunderson LH. called “Why systems of people and nature are not just social and ecological systems”
  • Resilience thinking takes a subjective rather than objective view of systems.  Being founded in systems theory, it aims to articulate the subjective perspective from which a system is analyzed to assist in the mapping and translating between multiple perspectives.
  • I believe that more data can help us  make the world more sustainable.  Data can show where theory is wrong, identify new problems, and suggest new ways of doing things.  Science and society don’t know how to create a sustainable society – consequently I believe we need to experiment, monitor, and observe to build a better world.
  • I don’t think resilience research lacks case studies.  Researchers in the Resilience Alliance has worked on a lot of case studies.   Ellinor Ostrom in particular has done a lot of compartive case studies.
  • Homborg writes that resilience researchers are trying”to develop a conspicuously and naively non-political cybernetic etiology of socio-ecological degradation – based on the assumption that such processes, irrespective of capitalist extractivism, are universally patterned, predictable, and potentially manageable.”
    The goal of my research is to help people make better decisions under conditions of uncertainty.  I want to better understand the dynamics of human dominated ecosystems – or social-ecological systems – not “subsum[e] social systems within the vocabulary of natural science”.   I am very interested in how people interact with ecosystems and I have tried to read and collaborate with a broad set of social and natural scientists to better understand social-ecological dynamics. As far as I know, none of the various social scientists I have worked with want to subsume the social sciences within the natural sciences but rather create new ways of understanding these linked systems, especially how they cope with change and surprise.

To response to specific questions:

  • Is “path dependence” so much better than various understandings of cultural, social, political, and generally structural problems of inertia and conservatism?
    Path dependence is a shorthand way of describing these things.   The term is general and not a term produced by resilience researchers.
  • What do we gain by rephrasing environmental conflict and armed resistance as “regulation”?
    Who does that?
  • How can we hope to predict and manage the abrupt surprises and discontinuities implied by notions of “critical thresholds” and “flipping”?
    That’s what resilience research is all about. There is a lot of active research on predicting “flips” (one recent example), with lots of papers being published on it in the last few years.
  • Why should concepts such as “non-linear dynamics”, “disturbance”, “opportunities for innovation”, “adaptation”, and “renewal” provide a better way of understanding what Joseph Tainter and many others for decades have recognized as socio-ecological collapse?
    While non-linear dynamics and disturbance and general terms from math and ecology, the other concepts are exactly what some resilience researchers have added to Tainter’s analysis.  Many resilience researchers are interested in how to avoid collapse and actively transform systems to new better states.  These concepts are new additions to our exploration of social-ecological systems.

Resilience researchers believe that because living in a human dominated biosphere, in which our way of life is destabilizing the ecological systems that stabilize our life support systems, learning how to be resilient to shocks and surprise are useful and important research goals.

I do this type of research because, I want to contribute to making human impacts on the biosphere positive rather than negative, and doing this requires a better, richer, understanding how social-ecological systems actually work.

Scenarios

Robert Charles Wilson on The Ruins of Tomorrowland

Leave a comment

Canadian Science fiction Robert Charles Wilson writes about shifts in the consensus vision of the future in The Ruins of Tomorrowland

This week ABC broadcast a two-hour documentary special called Earth 2100 that used art, narrative and interviews to sketch a doomsday scenario for the next 90 years. The problems the show enumerates—climate change, population pressure, and ever-fiercer competition for ever-scarcer resources—are inarguably real, though their consequences and potential solutions remain fiercely debated.

What struck me, however, as I watched Bob Woodruff walk us through the collapse of civilization, was how far our consensus vision of the future has evolved. Since when? Well, take as a baseline the year 1955, when TV viewers were exposed to another art-driven, scientifically-based panorama of the near future: Disney’s Man in Space, broadcast in three parts (Man in Space, Man and the Moon, and Mars and Beyond) on the Sunday-night program then called Disneyland.

For many viewers, Man in Space was probably their first systematic glimpse of space travel treated as a real-world endeavor. Producer-director Ward Kimball mapped out a scenario already long familiar to sf readers: how we would put a man into orbit, followed by the building of a space station, a landing on the moon, the exploration of Mars, and ultimately the launch of a fleet to the nearest star. …

We lived with that consensus future for the next couple of decades. Its apotheosis was the moon landing, and it unraveled along with the Apollo program, Skylab, the shriveling of NASA, and a dawning appreciation of the technical difficulty of prolonged manned space travel. Its legacy—one in which we can take great pride, I think, as a species—is the continuing robotic exploration of the solar system. We didn’t get that big shiny Wheel in the Sky, but we’ve seen the vastness of Meridiani Planum and the icy bayous of Titan’s methane rivers.

In the meantime the consensus future has shifted radically. ABC’s Earth 2100 is much the same kind of program, using art and narrative to sketch a scenario of what science leads us to expect from the future, but it’s more dismaying than Man in Space, the way a cancer diagnosis is more dismaying than a clean bill of health. What it tells us is that our civilization is teetering on the brink of unsustainability and collapse. Earth 2100 presents a scenario that ends with major cities flooded or deserted and a global population decimated by starvation and disease. (And God bless us all, as Tiny Tim might say.) Even the panaceas offered as consolation at the end of the program seem absurdly timorous: better lightbulbs and electric cars. In this world, Disney’s Tomorrowland is either a grotesque incongruity or simply a ruin.

Behind both visions of the future, however, there were and are unspoken caveats. The specter stalking Tomorrowland from the beginning was nuclear war. The implicit promise of Man in Space was not that its glittering future was an inevitability, but that it would be our reward if we managed to sidestep atomic annihilation.

And ABC has given us a stick rather than a carrot, but the implication is strikingly similar: this is what will happen if we are not wise, and prompt, and lucky.

It’s the continuing business of science fiction to explore these consensus futures and to challenge them. Optimism is still an option—we may indeed be wise and lucky—and, even in the worst case, the Earth 2100 scenario still leaves us with a human population and the possibility of creating something better than civilization as we know it.

And in the end the new consensus future will prove just as true, just as false, just as prescient, and just as absurd as was the Disney version. The only well-established fact about the future is that we can never completely predict it. Which is what makes science fiction such a useful and pertinent art. Even now. Especially now.

Big Back Loop

Limits to Phosphorus?

2 Comments

People have more than doubled the global flows of phosphorus, but unlike nitrogen, the other main fertilizer, phosphorus is mined. David A. Vaccari, an engineering professor from Stevens Institute of Technology writes in Scientific American about Phosphorus Famine: The Threat to Our Food Supply:

Altogether, phosphorus flows now add up to an estimated 37 million metric tons per year. Of that, about 22 million metric tons come from phosphate mining. The earth holds plenty of phosphorus-rich minerals—those considered economically recoverable—but most are not readily available. The International Geological Correlation Program (IGCP) reckoned in 1987 that there might be some 163,000 million metric tons of phosphate rock worldwide, corresponding to more than 13,000 million metric tons of phosphorus, seemingly enough to last nearly a millennium. These estimates, however, include types of rocks, such as high-carbonate minerals, that are impractical as sources because no economical technology exists to extract the phosphorus from them. The tallies also include deposits that are inaccessible because of their depth or location offshore; moreover, they may exist in underdeveloped or environmentally sensitive land or in the presence of high levels of toxic or radioactive contaminants such as cadmium, chromium, arsenic, lead and uranium.

Estimates of deposits that are economically recoverable with current technology—known as reserves—are at 15,000 million metric tons. That is still enough to last about 90 years at current use rates. Consumption, however, is likely to grow as the population increases and as people in developing countries demand a higher standard of living. Increased meat consumption, in particular, is likely to put more pressure on the land, because animals eat more food than the food they become.

Phosphorus reserves are also concentrated geographically. Just four countries—the U.S., China, South Africa and Morocco, together with its Western Sahara Territory—hold 83 percent of the world’s reserves and account for two thirds of annual production. Most U.S. phosphate comes from mines in Florida’s Bone Valley, a fossil deposit that formed in the Atlantic Ocean 12 million years ago. According to the U.S. Geological Survey, the nation’s reserves amount to 1,200 million metric tons. The U.S. produces about 30 million metric tons of phosphate rock a year, which should last 40 years, assuming today’s rate of production.

Already U.S. mines no longer supply enough phosphorus to satisfy the country’s production of fertilizer, much of which is exported. As a result, the U.S. now imports phosphate rock. China has high-quality reserves, but it does not export; most U.S. imports come from Morocco. Even more than with oil, the U.S. and much of the globe may come to depend on a single country for a critical resource.

Some geologists are skeptical about the existence of a phosphorus crisis and reckon that estimates of resources and their duration are moving targets. The very definition of reserves is dynamic because, when prices increase, deposits that were previously considered too expensive to access reclassify as reserves. Shortages or price swings can stimulate conservation efforts or the development of extraction technologies.

And mining companies have the incentive to do exploration only once a resource’s lifetime falls below a certain number of decades. But the depletion of old mines spurs more exploration, which expands the known resources. For instance, 20 years ago geologist R. P. Sheldon pointed out that the rate of new resource discovery had been consistent over the 20th century. Sheldon also suggested that tropical regions with deep soils had been inadequately explored: these regions occupy 22 percent of the earth’s land surface but contain only 2 percent of the known phosphorus reserves.

Yet most of the phosphorus discovery has occurred in just two places: Morocco/Western Sahara and North Carolina. And much of North Carolina’s resources are restricted because they underlie environmentally sensitive areas. Thus, the findings to date are not enough to allay concerns about future supply. Society should therefore face the reality of an impending phosphorus crisis and begin to make a serious effort at conservation.

Cities

Bicycles and Cities

Leave a comment

Many cities have been introducing public shared bike systems.  Montreal city just introduced a city bike system, Bixi, 300 station and 3,000 bikes.  The system allows you to check if bikes are available over the internet – and users pay for a subscription and longer bike rentals -less than 1/2 hr is free.  Stockholm has City Bikes, 70 stations and about 700 bikes, which work with a subscription for 3 hr rentals and are a partnership between an advertising company and Stockholm City.  Paris’s big Velib bike system started in 2007, now has 20,000 bicycles and 1,450 stations, and is a partnership with an advertising company.  These systems are part of an increased use of bicycles in western cities.

David Byrne, pop star and bicyclist, reviews Pedaling Revolution: How Cyclists Are Changing American Cities in the New York Times:

Full disclosure: I’ve ridden a bike around New York as my principal means of transport for 30 years, so I’m inclined to sympathize with the idea that a cycling revolution is upon us, and that it’s a good thing. Like Jeff Mapes, the author of “Pedaling Revolution: How Cyclists Are Changing American Cities,” I’ve watched the streets fill over the years with more and varied bike riders. It’s no longer just me, some food delivery guys and a posse of reckless messengers. Far from it.

That said, the revolution isn’t here just yet. Hedge fund managers and General Motors executives aren’t riding to work (though don’t laugh, they will), and this book is not likely to reach beyond the already converted, which includes me, other cycling advocates, and people in the city-planning and transportation universe. But the book is useful — for those of us who occasionally find ourselves on the defensive, Mapes provides names, dates, facts and figures. He details how cities from Amsterdam to Paris to New York to Davis, Calif., have developed policies encouraging cycling in recent decades, and how other towns are just beginning to make way for bikes. He lays out in an easily digestible way a fair amount of material on trip patterns, traffic safety and air pollution. He quotes the relevant studies and shows how those studies have been either heeded or ignored. All this information is great ammunition for those of us who would like to see American cities become more bike-friendly but may be a tough sell for the people on the fence — the ones who’ve taken the occasional Sunday ride along a riverfront greenway or in a park, or have a vague feeling that they might possibly bike to work somehow someday.

…

Mapes finds the experience of riding around Portland — North America’s most bike-friendly city (though I think Vancouver is close) — so enjoyable that he takes as a given that it’s a positive thing, something that more communities should accommodate without question.

Visualization

Climate change theatre

3 Comments

There has been a lack of art that addresses climate change, and this lack reduces the ability of people to envision possible futures and consequently make better decisions today.  This appears to be changing.

Playwright Steve Waters double play – Contingency Plan: On the Beach/Resilience focuses on science and politics of climate change.  The Observer writes Writers and artists are getting warmer

It is a striking stage experience. A group of cabinet ministers and scientific advisers, part of David Cameron’s newly elected government, gathers in a Whitehall basement to monitor a storm of unprecedented violence that is sweeping Britain. High seas, engorged by melted ice caps, threaten the country. Reports of gales, flooding and stricken communities pour in. Then, abruptly, the emergency telephone lines go dead and the lights fail. The tiny upstairs theatre at the Bush, London, is plunged into total darkness. Outside, a nation is drowning.

It is riveting stuff, though it is not climate change itself that forms the core of Steve Waters’s Resilience. It is the human and cultural reaction to it. “Who supplies us with electricity?” demands an infuriated minister in the pitch black. “EDF! Christ, I have got fucking shares in EDF.” Thus a national crisis becomes a battleground of self-interest, political ideology, buck-passing and bungled responses to scientific warnings.

According to Guardian theatre critic Michael Billington, Resilience has no theatrical rival for its emotional intensity at present and I am sure he is right. The play, with its partner work, On the Beach, is absorbing, intelligent, daringly imaginative and superbly performed. What really intrigues, however, is the fact that this is the London stage’s first serious attempt to tackle the issue of climate change and its impact on society.

Cities

Urban agriculture and the past’s toxic legacies

Leave a comment

Urban gardening with lead’s legacy, from the New York Times For Urban Gardeners, Lead Is a Concern

If soil is found to have high levels of lead, experts advise covering it with sod. Those who want to grow flowers or edible crops can either replace the contaminated soil or alkalinize it by adding lime or organic matter such as compost. Soil with a pH level above 7 binds with lead, making it less likely to be absorbed by plants and the human body if the dirt is inadvertently inhaled or ingested.

..Dr. Filippelli recommends planting kitchen gardens with fruiting crops like tomatoes, squash, eggplant, corn and beans because they don’t readily accumulate lead. Lead-leaching crops, he said, include herbs, leafy greens and root vegetables such as potatoes, radishes and carrots. Dirt also clings to these crops, making it hard to wash off and thereby increasing the risk of ingesting lead.

But some experts advise planting greens, specifically Indian mustard and spinach, for a couple of seasons as phytoremediation, or plant-based mitigation, before growing crops intended for food. By growing spinach for three months, researchers at the University of Southern Maine lowered the lead count in one garden by 200 p.p.m. Of course, the lead-leaching crop cannot be eaten or composted and must be disposed of as toxic waste.

A safer approach, particularly in areas where lead levels exceed 400 p.p.m., is to build raised or contained beds lined with landscape fabric and filled with uncontaminated soil. Luckily for Mr. Meuschke, many of his edible crops are in containers or pots filled with dirt bought at nurseries.

But lead dust blowing in the wind or rain splashing off lead-painted structures can sully food grown even in raised beds or containers. Situating gardens away from buildings is therefore a good idea, as is washing produce thoroughly with water containing 1 percent vinegar or 0.5 percent soap.

“It isn’t that you shouldn’t garden if you find lead in the soil, you just have to manage the space,” said Edie Stone, executive director of GreenThumb, a division of the New York City Parks and Recreation Department that supports urban gardening.