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The social and ecological footprint of a carne asada taco

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What is the ecological footprint of your lunch today? Seriously, think about what you brought with you, or where you went out to today. How much land was required to grow the crops or raise the animals involved? How much water did they require? What additional processes go into that food beyond just growing it, like the oil burned to ship ingredients to you?

Driving in to Hermosillo for a visit last year, the view through my windshield at a traffic light.

Driving in to Hermosillo for a visit last year, the view through my windshield at a traffic light.

If you live in Tucson or in Hermosillo (or really in any city with increasing food cart culture now), your routine might include a visit to the nearest taco cart for some carne asada. And a team of researchers have now calculated the ecological footprint of all the carne asada from taco carts in Hermosillo. Their results will appear in a special issue of the Journal of the Southwest this fall.

Carne asada, as I recently learned from two of the authors, Nemer Narchi of ColMich and Alberto Burquez of UNAM in a presentation about their research, has a more specific cultural history and context than just beef that is grilled. This particularly North Mexican dish is a specific process of grilling beef on mesquite charcoal and is a relatively recent culinary invention dating from Jesuit arrival. Carne asada is typically served on wheat tortillas instead of corn tortillas. The article traces the way cattle and wheat together were major agricultural introductions that settled a traditionally nomadic indigenous dominated north, allowing it to be incorporated into the centralized Mexican state. As mining and cattle culture spread, carne asada served alongside tortillas and salsas was born from family celebrations after butchering cattle to serve miners in mining camps. As the population of Northern Mexico became more urban, unemployed butchers during recession cycles opened mobile restaurants serving snack-sized combinations of these ingredients: the taco carts.

A cow standing in a converted buffel grass pasture. I took this photo while visiting Alberto last year, near one of his study sites outside Hermosillo.

A cow standing in a converted buffel grass pasture. I took this photo while visiting Alberto last year, near one of his study sites outside Hermosillo.

The researchers then calculate the environmental and socioeconomic costs of the industry that has formed to produce the now ingrained culinary traditions. When you eat carne asada from a taco cart in Hermosillo, the cattle were likely raised on the extensive ranches surrounding the city. Throughout the state of Sonora, ranch lands are being converted from native Sonoran Desert thornscrub plants, including native grasses, to bulldozed and planted pastures of a grass introduced from Africa, known as buffel grass (Pennisetum ciliare). Yes, this is the grass that I have been studying for a good part of my dissertation research. It has a large effect on the native plant species. Between the bulldozing, the buffel grass planting, the water required, and the potential erosion and other effects of overgrazing, cattle ranching in Sonora to produce the legendary carne asada can have a heavy footprint, as well as a large one.

And then you must consider the wheat grown to produce the tortillas. And the native mesquite trees cut, frequently from ecologically fragile riparian areas, to produce the mesquite charcoal used to grill the beef. So what is the final footprint? You’ll have to check out their article this fall or some recent press coverage for more details.

A heavily grazed area that is not planted with buffel grass.

A heavily grazed area that is not planted with buffel grass.

But almost more importantly, this research focuses on the footprint of everyday objects, and provides a model for how to start researching that. You can plug your life statistics into online calculators to find out your overall ecological footprint, but it feels a little more abstract than knowing what this one taco required some specific amount of acreage and, increasingly importantly, some specific amount of water. They also examine why that footprint is what it is, what social and economic choices and policies and trends shaped that footprint.

What are the footprints of the small pleasures and cultural anchors of your daily life? What would be your taco cart if you were to follow the lead of Nemer, Alberto, and their coauthors, to find out what something you consume regularly costs ecologically and why it is made that way?

A neat view out my car window as I drove through Hermosillo last year.

A neat view out my car window as I drove through Hermosillo last year.

Written by pacificsummer

July 20, 2015 at 10:54 am

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Luminous footsteps of the dancing desert mice

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The protocol: Trays of seeds and fluorescent yellow powder are placed at sunset with a game camera to record who tracks the powder around.

The protocol: Trays of seeds and fluorescent yellow powder are placed at sunset with a game camera to record who tracks the powder around.

I can hear the cicadas buzzing outside, so I know it must be hot. The predicted high on NPR at dawn this morning was 99 degrees Fahrenheit. Not so warm for June in the Sonoran Desert, but uncomfortable. My fieldwork for several summers involved starting at dawn, but staying out all day in this, marking little seedlings on exposed hillsides. (You can see very preliminary – not peer reviewed yet – results of what I found at the Southern Arizona Buffelgrass Coordination Center website.) All summer. It was, well, tough. I have a rather unique data set as a result.

I was listening to the NPR weather report at dawn today because I was on my way to a field site to retrieve some plastic trays of seeds coated in fluorescent powder I had left out all night before. I am interested in the places nocturnal seed-eaters go. The wind picks up during the day, so I wanted to minimize the powdery spray between the time the seed eaters tracked it around, and when darkness falls and I can return to trace their pathways with blacklights (and friends!). I explained a little about the goals of the project in my previous post.

Looks like this tray got a visit! All the seeds are gone and there are scratch marks in the fluorescent powder, then tracks to the side of the tray...

Looks like this tray got a visit! All the seeds are gone and there are scratch marks in the fluorescent powder, then tracks to the side of the tray…

This dawn and dusk schedule is much more comfortable, convenient for me getting other writing done during the day, and also for attracting volunteers. Many animals adopt this schedule in hot deserts. The schedule even has a name: crepuscular, although I call it the siesta schedule. This will be key because I am detecting fewer pocket mice per night than I had hoped. So I may be in for many more crepuscular days of leaving little offerings to the desert, trying to increase my sample size.

Here is a teaser of the pocket mouse (genus Chaetodipus) jamming the fur-lined pockets next to its mouth full of seeds, then burying them nearby like a pirate with treasure, or a squirrel with nuts. Most animals that “scatterhoard” their seeds in many small caches near the source later return to move them to secondary caches, or even eventually to their “larder” in their burrow. I suspect these pocket mice behave in a similar way.

And as a bonus, when the little guy (or gal) first showed up, before eating anything, it did my favorite “dancing” behavior:

Was it marking this resource for itself? Attracting a mate? Doing an instinctive behavior in response to positive stimulus? We need an animal behavior specialist to get on testing this.

And a few last gratuitous shots of the experimental set-up during a beautiful Tucson sunset:

SONY DSC

Trays of seeds and fluorescent yellow powder are placed at sunset with a game camera to record who tracks the powder around.

Written by pacificsummer

June 7, 2015 at 10:51 am

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Some awkward footage of an interesting animal

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Ever wondered what a javelina (Pecari tajacu, syn. Tayassu tajacu) looks like from underneath? Yeah, me neither.

The setup: a seed tray dusted with fluorescent powder and a game camera to find out who tracked it about.

The setup: a seed tray dusted with fluorescent powder and a game camera to find out who tracked it about.

I did wonder, however, whether pocket mice (genus Chaetodipus, yes, the dancing ones), known for foraging under cover to avoid predation by owls, would tend to bury palo verde or other seeds under buffel grass (Pennisetum ciliare). Buffel grass is an invasive bunch grass spreading through the Tucson Mountains that inhibits native seedlings from establishing – and provides some nice cover to these mice, potentially attracting them to bury native seeds in the worst possible place: right under buffel grass.

To test this hypothesis, I left fluorescent-dusted seeds on fluorescent-dusted trays in the desert to see where mice would take the seeds, planning to return tonight with UV flashlights to follow their luminous footsteps. It felt like leaving sunset offerings to the tiny, dancing desert gods.

Much like the fantasy world of Game of Thrones, however, the Sonoran Desert has many gods who are more than happy to accept offerings. Most seed trays, it turned out, were visited by a roving band of javelina. Check it out:

You get a great view of their four-toed front feet, of their flexible snout at work, at their lumbering gait, and their curious investigation of the seed trays, marking flags, and cameras, and their powerful molars grinding the seeds of the foothills palo verde (Parkinsonia microphylla). One of the major reasons scatterhoarding rodents like pocket mice may be beneficial for the trees is that they protect some seeds from destructive consumers, like javelinas.

Often thought to be pigs, javelina are in a different family, although still related. This is an animal that is hunted for sport and meat, and is seen as a menace and a pest as it roves through town, knocking over trash cans. It lives in a wide variety of habitats, including even cloud forests and swamps as far south as Ecuador. Check out more information on them from the Arizona-Sonora Desert Museum, or visit in person to see some javelina yourself.

Written by pacificsummer

May 26, 2015 at 9:43 am

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A scaly problem

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Driving down the Catalina Sky Highway from the summit of Mount Lemmon, Tucson looks at first like a dusty blond blur. As you approach the base of the mountain, patches of brilliant lemon resolve themselves.

A good year for palo verde trees is a bad year for allergy sufferers.

A good year for palo verde trees is a bad year for allergy sufferers.

As anyone with allergies knows, the palo verde trees (genus Parkinsonia) are blooming in force right now. But which neighborhoods are so infused with the native trees? Where do they start and end? From thousands of feet up, drawing patch lines seems trivial, but walk through the streets under the branches themselves, and you feel less certain. Is this block in, or does the patch start one more over?

You may begin to notice patches even within neighborhoods. At what scale should the palo verde patches be drawn?

The patch size of interest probably depends on your question. If you are seeking palo verde trees in Tucson to photograph (or seeking to avoid their pollen), a map with the raw number of trees per block might be helpful without trying to draw lines around patches. So why bother delineating these categorical zones at all? Why not measure some continuous variable, such as the number of palo verde trees on the block?

In other cases, a patch size itself is an important variable, so you have to stand back, squint your eyes, and draw the lines. The local invasive bunch grass buffel grass (Pennisetum ciliare), for example, grows outward in roughly circular patches. To track the rates of its spread in the foothills of the Santa Catalina Mountains, researchers have used repeated aerial photographs and traced polygons around the visible buffel grass patches.

SONY DSC

We got into a snowball fight with an infrared game camera used for detecting wildlife on our mountaintop campus.

I just returned from four days at UA Science Sky School, where we had snowball fights between the pines and aspens! There are no palo verdes to be seen on top of Mount Lemmon, which is a Sky Island, a little patch of pine forest in a desert sea. But where does that patch boundary lie? In fact, the vegetation changes in several dramatic and distinct zones as you travel up the mountain, but trying to pinpoint the transition point is an exercise in frustration.

The groups of students from Flowing Wells High School that I mentored this week at Sky School also had to confront these questions as they conducted field-based scientific research. To answer their question about how resources for plants (and animals) changed as a result of forest fire, we needed plots on either side of a burn boundary. The boundary of a fire seems abundantly clear until you are forced to locate a 10m x 10m plot right along that boundary.

Fortunately, the students in my group were focused on what characteristics mattered for their question. The question of where a boundary lies, at what scale, can be a very scaly problem indeed, and they resolved it by drawing a thicker boundary line between the burned and unburned areas, on either side of which the light, vegetation, and water availability was less affected by proximity to the other type of area.

SONY DSC

Two students take a soil sample for measuring percent moisture.

Written by pacificsummer

April 26, 2015 at 12:03 pm

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Do people like you belong in the backcountry?

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Well, do they? Take a moment to answer that.

Honestly, answer it. Here are a couple beautiful photos my friend Ty took to enjoy while you think about it:

This photo casts serious doubt on whether I belong in the backcountry. (That's me doing "the walrus" up on to a redrock ledge in The Maze last January.)

This photo casts serious doubt on whether I belong in the backcountry. (That’s me doing “the walrus” up on to a redrock ledge in The Maze last January.)

A night camped on the Green River means pooping in bags and packing it out. Do you have what it takes?

A night camped on the Green River means pooping in bags and packing it out. Do you have what it takes?

What did you answer? And what did you take “people like you” to mean?

Your answer might depend on who you see represented in ads for outdoor brands, or in films at the Banff Mountain Film Festival, or who you see out on trails.

Or how often you yourself get outside.

There are lots of reasons some groups get out and enjoy nature more than others, which are beyond the scope of this post, but one factor is income (which is, of course, connected to many other factors). If you don’t have the money for a car (or gas, or gear) or the time off of a low-paying job, it can be hard to take your family to the nearest national park or wilderness area. If you’re not very healthy, or you have a hard enough time with daily life, the idea of tackling an optional challenge – physical exertion in a strange new place – may seem like a luxury.

And if you never have been out hiking, it’s sure hard to imagine yourself doing it. One way to solve that is to give more people (kids, families, everyone) the opportunity to leave the city and experience nature.

You think we're going to climb down WHAT to get to that river?

You think we’re going to climb down WHAT to get to that river?

I volunteer with an organization through the Sierra Club, that recently changed its name from the 30 year old “Inner City Outings” to “Inspiring Connections Outdoors,” but the goal of the all-volunteer nonprofit is to give kids an opportunity to experience nature who might otherwise not get out of the city. Volunteers who have passed background checks and been trained in outdoor skills and first aid partner with Title I Schools, halfway houses, and other groups that work with at-risk and underprivileged youth to provide opportunities to go hiking, caving, camping, and stargazing.

The primary expense the group has is transportation costs for the kids, although when we can, we like to provide healthy snacks so everyone has had more than a bag of Hot Cheetos to fuel their adventure.

A group of MBA alumni from Arizona State University that have an annual tradition of hiking the Grand Canyon Rim 2 Rim 2 Rim (47 miles and change… and a lot of elevation change!) are using their trip to raise money for this group. I appreciate these guys who feel they belong in the backcountry raising funds (and awareness) to help a new generation expand that pool of people who feel they belong there, too.

Want to kick in to support getting underserved youth outdoors in the Tucson area? Donate to their campaign: https://www.crowdrise.com/r2r2r2015/fundraiser/

And in somewhat a related note on representation in the outdoors community, for women who are annoyed that skis made for women’s sizes and shapes are often of lower performance aimed at intro-level skiers and snowboarders rather than the advanced and expert, check out this kickstarter of high performance skis and boards for women (sans the pink flowers, as a bonus!):

But it was a nice paddle once we were down.

But it was a nice paddle once we were down.

Written by pacificsummer

March 25, 2015 at 11:01 am

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Energy and sexual activity: the data says…

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Kangaroo rat pups born in a trap overnight (they are covered with millet from being dumped out of the trap).

Kangaroo rat pups born in a trap overnight (they are covered with millet from being dumped out of the trap).

Back in January, I speculated on this blog about some disorganized observations I had made of unusually high rodent reproductive activity (resulting in pups born in traps overnight in February).

Since I followed that with a post on the importance of systematic data collection, rather than relying on a series of anecdotes, I should probably follow my own advice and provide some data analysis on the rodent reproduction.

Fortunately, the observations I wrote about in January were made at the site of a long term experiment on the interactions of rodents and plants. Ecologists have collected thirty-eight years of data on rodent reproduction, along with systematic data on weather and plant life.

Base camp for the long term project started by Jim Brown in 1977.

Base camp for the long term project started by Jim Brown in 1977.

Erica Christianson, a doctoral student at Utah State University, is studying these interactions at Portal as part of her dissertation work, and she crunched some of the numbers on reproduction and weather conditions (and generously allowed me to share them here!).

Erica’s main hypothesis, and one I wondered about in January, was that the large rainfall in the late summer and early fall last year resulted in more seeds available in early winter. With sufficient energy to stay warm and active during the winter, females could afford to breed.

A very quickly constructed scatterplot reveals that years with higher rainfall in the late summer and early fall do indeed have higher rates of female reproductive activity observed the following January:

Precip&Repro2

You might notice a couple of things about this plot. First, you would be justified in pointing out that this is a correlation, and does not prove that the summer rain causes high January rodent reproduction. But it is consistent with a reasonable explanation for it.

You might imagine designing an experiment to test the causality more directly, in which all the plants are killed before they produces seeds after the next year with high summer rainfall. That would be an ambitious experiment on this landscape, involving a lot of person-hours with some herbicide or clippers, but it could be done.SONY DSC

You might also notice that fall precipitation does not perfectly predict female reproductive activity. Probably that interacts with several other factors. Ever noticed how you get hungrier in cold weather? Your body burns more calories to stay warm. (This is why mountaineers are advised to continue eating as much as possible if caught out overnight on a cold peak.) I suspect that if we also looked at the temperatures each winter, we might find that less rain is required in warmer winters to boost female reproduction, and the rainfall plus temperature would explain even more of the variation in reproductive activity. But that probably best left to future posts.

A lot of grass grew in the San Simon Valley following heavy late summer rains, providing substantial seed resources this winter.

A lot of grass grew in the San Simon Valley following heavy late summer rains, providing substantial seed resources this winter.

I should also point out that these results are extremely preliminary. Typically, to have some confidence in a conclusion, the full description of the methods for data collection and analysis should be subjected to peer review – that is, at least three or more other experts will critique it before it is published. That’s definitely not how my blog works.

If you are interested in getting out in the field to collect data used in real long term and large scale research projects, check out iNaturalist, National Phenology Network, and the Arizona Sonora Desert Museum. If you are in Tucson this weekend for the Tucson Festival of Books, visit Science City to meet some of these folks in person and pick up brochures for other Citizen Science opportunities as well!

One last photo: a cactus mouse (Peromyscus eremicus) that was released and immediately climbed the fence supposed to keep the rodents larger than that out. Let's hope the kangaroo rats are less bold.

One last photo: a cactus mouse (Peromyscus eremicus) that was released and immediately climbed the fence supposed to keep the rodents larger than that out. Let’s hope the kangaroo rats are less bold.

[Updated 3/17/15: I changed the label on the x axis of the grass from “Fall precip” to “late summer” to more accurately reflect how the plants seemed to respond to the rainfall and be more consistent with my text.]

Written by pacificsummer

March 12, 2015 at 9:51 pm

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The plural of “anecdote” is not “data”

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Students from Flowing Wells Jr High attending UA Science Sky School don't just make anecdotal observations: they take measurements in a variety of environments (leaf litter in burned and unburned sites).

Students from Flowing Wells Jr High attending UA Science Sky School don’t just make anecdotal observations: they take measurements in a variety of environments (leaf litter in burned and unburned sites).

I first heard this phrase from my friend, Brad Boyle, last weekend (though he was cheekily commenting that the plural is data). An anecdote, in case you’re not sure, is a story about something that happened, usually to you or someone you know. It might be something you noticed once, or even a number of times. And that provides you with some information. But that does not necessarily make it data.

Data is information that should be collected and analyzed in a standardized way to answer a question or estimate some value (like the growth rate of a population or the strength of a bridge). One problem with anecdotal information is that it is not collected with the intention of providing a large or unbiased sample. Basing our understanding of the world around us on anecdotal information could lead us to the wrong conclusions, resulting in poor decisions.

For example, many medical procedures have variable outcomes. Imagine you have some inflammation of the elbow (lateral epicondylitis) from playing tennis, rock climbing, or just everyday life. Corticosteroid injections seem to be the most effective way to get a short term reduction in pain and inflammation so that you could use that elbow in the next few weeks. However, the study I linked to reported a 92% success rate at the six week mark. What if you had a big competition coming up and wanted to decide whether to go for the treatment? If you talk to only your aunt, who had had the procedure, and was part of the 8% it did not help, you might decide not to get it. Especially if you heard a second anecdote from your best friend, who was also not helped! There you have multiple anecdotes, but a larger sample might reveal there is a pretty good chance it would help you be able to compete.

Understanding the scientific method is important for everyone, not just scientists. If your vacuum cleaner breaks, to borrow an example from another friend, Marielle Smith, scientific thinking can help you to fix it more efficiently. Instead of replacing parts at random, you might form a hypothesis about what piece failed. That hypothesis might be based on anecdotal information, like what part of your friend’s vacuum cleaner broke. Or it might be based on observations, such as where smoke is emerging from. Either way, you can test your hypothesis by isolating that part of the vacuum to test it, or by replacing it and trying the vacuum, ultimately spending less time and money than replacing parts at random.

The same students from Flowing Wells presenting graphs of their data at the Sky School Symposium. (They even have error bars on their graphs!)

The same students from Flowing Wells presenting graphs of their data at the Sky School Symposium. (They even have error bars on their graphs!)

Helping each other to better understand science and the scientific method is important for all of us, as well. With outbreaks of preventable diseases, like measles, currently happening in the United States, we can see the negative effects that not vaccinating children has on those who are too young or sick to be vaccinated. The data shows that vaccines are safe and measles are not, but some parents are scared anyway. With 2014 the warmest year on record (though one year does not a trend make), we more urgently need political action on climate change than ever, but a large proportion of the US electorate first needs to better understand the risks of unchecked climate change.

So what can YOU do to increase scientific literacy?

1. Practice asking questions.

Question everything. Question sources, and learn who has the expertise to be right about a subject. Just as a theoretical ecologist might not have the skills to remodel a kitchen professionally, a lobbyist with no scientific training may not have the skills to validly contest a research finding. Make up questions while you’re driving (or biking) to work, or waiting in the grocery store check out line. Just be curious about the world.

2. Practice answering questions.

Design a way to collect data to answer them, even if you do not intend to hang out at the grocery store all day collecting that data, or use Fermi estimation to get close. Why? It’s more entertaining than watching the driver singing (or worse) in the car behind you, and as my junior high math teacher always said, it’s like going to the gym for your brain. (If you enjoy this kind of problem,  you will really enjoy the What If? page of xkcd.com.)

3. Learn the difference between causation and correlation (and more about trends, variability, and probability in general).

To use the famous example, both ice cream consumption and murder rates go up during the summer, but that is probably not because eating ice cream makes people want to murder each other. I spend a lot of time these days analyzing data I collected for my dissertation, and discussing probability and analyses with other graduate students. We have to formally analyze data because human brains are not really wired to understand probability. The more you can learn about this, and how to bolster your own ability to understand and communicate about variable results, the better you can interpret the world around you.

4. Interact with scientists and science educators at your local university.

If you live in Tucson, check out the Cosmic Origins lecture series, which is free and open to the public (but crowded – get there early!), or Science Cafe talks at local breweries and restaurants. Visit the Laboratory of Tree Ring Research, see a laser show at Flandrau Science Center and Planetarium, use the telescopes on Mount Lemmon during SkyNights programs or with Sky School, tour Biosphere 2 or the Mirror Lab, or hike up Tumamoc Hill. The Gem and Mineral Show is going on now – find the UA Geosciences students teaching there! And Tucson Festival of Books has a whole Science City where you can see rockets, volcanoes, gila monsters, and more – for free March 14-15. Even better, volunteer for Science City this year (they still need many, many volunteers)!

5. Support science fairs.

Whether you’re a parent who can encourage your kids to do an experiment, or a scientist who can volunteer to judge, get involved! In Tucson, the regional Southern Arizona Research, Science and Engineering Foundation Fair is coming up!

6. Use science to shape how you communicate with people around you.

There are very rational reasons that people may not have all the data or scientific interpretations on a topic, like vaccinations. Going out and doing research takes time and effort, and people have lives to live. Researching every little thing is impossible. So instead, we lump issues together into our identities to decide how we feel about them. Cognitive science has demonstrated that attacking a person’s beliefs, or implying that she or he is an idiot for not knowing something, is the best way to solidify a previously held belief. So when engaging with someone less scientifically literate than you, use what evidence suggests is the best way to get them to change their beliefs: acknowledge their fear or doubt are real and reasonable, acknowledge that data and scientific papers are often not open access, and… ask questions.

Written by pacificsummer

February 4, 2015 at 10:47 am

Posted in Uncategorized

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