A map of swine feeding operations in Iowa, with a big concentration in the state’s northwest corner. From Christopher Jones’ presentation to the Iowa Academy of Science.

When it comes to manure, research engineer Christopher Jones of IIHR – Hydrosciences & Engineering at the University of Iowa has a knack for putting quantities and consequences in stark terms.

In blog posts earlier this year, Jones calculated how much animal waste Iowa’s millions of hogs, cattle, chickens and turkeys produce – an amount equivalent to 134 million humans – and where that puts us in the manure hierarchy of U.S. states.

The data caused a stir, with The Des Moines Register and other media playing up the implications. Now you can hear Jones discuss his findings in person.

March for Science Iowa is bringing Jones to West Des Moines’ Twisted Vine Brewery, 3320 Westown Parkway (just off Interstate Highway 235) on Wednesday, August 7, for a discussion over snacks (free), microbrew beer (on your own) and soft drinks. We’ll gather starting at 6:30 and begin the program at 7.

It’s one of two science-driven events worth your attention in the coming week.

Jones’ research focuses on water quality and agriculture and he helps manage a network of water-quality sensors in streams across the state. I first heard him in April at the annual meeting of the Iowa Academy of Science, where he was one of three speakers on Iowa water quality.

Jones and others at the U of I calculate it, Iowa has just 4.5 percent of the land in the Mississippi River watershed and contributes just 5.9 percent of the water flowing to the Gulf of Mexico – but generates an average of 29 percent of the river’s nitrate load.

There are several possible reasons for this, including farm drainage through tiling. But Jones also noted that animal operations and commercial fertilizer play big roles. For example, northwest Iowa has the state’s largest concentration of animal feeding operation and some of the highest commercial fertilizer use. Two rivers that drain that region, the Rock and Floyd, also have the state’s highest nitrate levels.

Which brings us to Jones’ calculations of Iowa’s animal waste load. Working with colleagues, he calculated the distribution of animal feeding operations and human population among the state’s major watersheds. Some farm animals, especially pigs, produce prodigious amounts of manure – many times that of human output. Iowa’s population of 20 million to 24 million hogs is the waste equivalent of 83.7 million humans, Jones figured. Dairy and beef cattle produce feces equal to that generated by another 33.6 million people and laying hens and turkeys add droppings on a par with about 16 million humans.

Hogs, cattle, laying hens and turkeys produce manure equivalent to the human population found in many of the world’s major cities. From Christopher Jones’ presentation to the Iowa Academy of Science. Click to enlarge.

It adds up to a mountain of feces equivalent to that produced by a human population of about 134 million, Jones estimated. (He later updated that to 168 million after new animal population data came in.) And, unlike human waste, almost none of it is treated; most is spread on farm fields.

The cap to Jones’ talk was the jaw-dropping map he devised to equate Iowa’s waste-producing population by watershed with the equivalent populations of states and cities, in the United States and around the world. It’s astounding: The animal population in northwest Iowa’s watersheds produce as much waste as four of the world’s most populous cities: Bangkok, London, Mexico City and New York City – plus all of Iowa.

It’s a startling illustration, but Jones’ talk and the blog post on which he based it got little attention until June, when, in another post. he calculated how Iowa’s manure load – the fecal equivalent population – compares with that of other states. We’re at the top – not necessarily something to brag about.

Jones is careful to state that he’s not making value judgments about all this. He recognizes how important agriculture is to Iowa. But he has thoughts on what policies are needed to improve the state’s manure management and water quality. I hope he’ll share those with us next week – or that his talk will prompt questions on the subject. Tickets are not necessary, but we’d appreciate it if you’d RSVP.

Before we get to the main event, however, March for Science Iowa will have a (hopefully short) business meeting to determine the organization’s future. We’re sorely lacking in volunteer power and can’t continue to hold events like this, the Science Festival Trail and Science on the Stump without people dedicated to science in the public interest and evidence-based policy stepping up to contribute a couple of hours a week, on average. We need you.

Meanwhile, there’s more science next week when SciLine, the science information bureau for journalists I wrote about nearly a year ago, returns to Iowa. Their big event, Climate Change: Rising to the Challenge, is Tuesday August 6 at 6:30 p.m. (doors open at 6) in the Science Center of Iowa planetarium in downtown Des Moines. Three state climatologists, including Justin Glisan of Iowa, will talk about the climate trends they’ve seen, what the future may hold and how they’re working to protect the citizens they serve. PBS science correspondent (and longtime science reporter) Miles O’Brien will moderate.

SciLine director Rick Weiss says the panel is the final event of Science Essentials for Political Reporters, a 2½-day boot camp for 32 political campaign reporters, staged in cooperation with the Drake University School of Journalism and Mass Communication. They’ll learn about the latest peer-reviewed science behind major issues sure to come up in the Iowa Caucus campaign, he says.

The Science Center event is free, but space is limited and registration is required. Go the link above to get your ticket. Then come out to the Twisted Vine on Wednesday. No ticket required, and you can have a beer while contemplating manure.