Our research and blog were recently featured on CU Boulder Today. Read the article here.
Our research and blog were recently featured on CU Boulder Today. Read the article here.
We are back in the U.S.A. after a very successful trip. I’m excited to share another science-focused post soon, but with the jet lag that definitely won’t be today!
Since we had limited internet access from the field, I have a backlog of pictures to share. Here’s some highlights of the desert landscape. The valley, filled with fairy circles, surrounded by mountains and dunes made for a stunning background and incredible sunsets.
As female scientists we are inspired, humbled, and grateful for the global outpouring of support for science from our colleagues, friends, and family. Although we have been doing field research the last two weeks in the far reaches of Namibia, we are with you in solidarity today!
We are nearing the end of our fieldwork, and I’ve learned so much about working in a rural setting and in another country. The rural location means that there is a lot of driving most days—especially anytime we want to check out a new potential site. There is one main road through the reserve, but most of the time we are on 4-wheel-drive back roads that aren’t open to the public. We’ve learned a bit more about driving on dunes and through heavy sand—lower tire pressure, stay in second gear, keep your RPMs at 250, and keep up momentum…but not too fast (there was a steep learning curve for those last two and we ended up going too slow several times and having to back down the dune to try again)!
One of the amazing perks is that, in essence, we lead our own private safari drives when checking out new potential field sites and driving on the 4-wheel drive roads. Oryx and zebra are everyday sights, and we’ve also seen jackal and ostrich. On one of our first drives, we came across a dead Oryx with four jackals having quite a feast. It was an amazing sight to see! On another day we saw an ostrich with eight babies. They crossed the road right in front of us. Holly has become an ostrich feather seeker, and we have quite a collection in our truck to go along with the various grass specimens we’ve collected to identify on this trip to the wardens’ house.
We’ve been really fortunate to be able to stay on the reserve during our time here. They have several old ranch houses that are a mix of privately owned and now owned by the foundation. The houses all use solar power and have giant tanks of water that are trucked in. We ended up switching houses a few days ago since our power stopped working at the old house and it takes a long time to get the parts (at least a month in this location). While the move was a hassle, the new house is definitely an upgrade! It has a beautiful deck overlooking a watering hole, which is where we spend most of our evenings. There is a leopard currently using the waterhole by the house. While we haven’t been lucky enough to see her, we know she came by the house last night and was roaming around the dune right by Nichole’s window.
The house is built right next to the dunes to the point that the dunes are overtaking it in some locations. For example, the porch roof is only about 6 feet off the sands, as the area has filled in with the red sand of the dune system right behind it. I’m not sure where the house was in relation the the constantly shifting dunes when it was originally built, but right now it is an odd mix of the most beautiful location imaginable, but not very practical where it is impossible to keep the house sand-free for more than a half day.
We spent much of the morning looking at our experiment treatment sites that Nichole Barger, Mike Cramer, and Walter Tschinkel originally set up in 2015. The experiment tests a few of the hypotheses (see post 1) for why fairy circles might form. We test these multiple competing hypotheses by trying to do the opposite of creating fairy circles— in other words, we are trying to “kill” them. The idea is to apply different treatments and see which ones allow fairy circles to fill in with new recruits (thus killing the fairy circles as they fill with grass, removing any spatial patterning).
A Little Background
In a fenced in area that was initially created to keep the animals from ruining any equipment, Nichole, Mike, and Walter applied a treatment of water or water + fertilizer to some of the circles. Others were left alone as controls. And still others were treated with an insecticide to kill the termites within the circles.
Outside of the fence, we have additional control sites that received no treatments and are accessible to herbivores (mainly Gemsbok Oryx, Springbox Oryx and zebra here).
The site was set-up approximately a year into the drought. Since then, it hasn’t received any measurable rainfall until just a month ago or so—the reason for this trip.
The Current Story
After getting the lay-of-the-land, we were excited to return to the sites and scope them out. While the next several days are devoted to more detailed measurements, we wanted to stop by right away and just get a sense for what had happened to the circles. Our first circle looked similar to back in 2015…but as we walked around, it became clear about 2/3 of the circles within the fence have started filling in. Some have a few young recruits in the center, while others have many, many recruits!
Surprisingly, we didn’t notice a strong signal of any of the treatments within the fence, though maybe one for the watering + nutrient treatment.
The striking pattern is that herbivores seem to play a critical role in maintaining fairy circles. None of the circles outside of the fence have recruits within them, but many of those inside the fence are filling in—even in the controls! Herbivores indeed seem to be playing a critical—and perhaps overlooked—role in this system. While they likely don’t create fairy circles, our first stop at the site seems to say that they definitely do help promote the long lifespan of fairy circles. We are heading back to the site tomorrow to begin collecting more detailed measurements.
After three days of travel, we have finally arrived in NamibRand
Nature Reserve. We traveled from Colorado to Washington D.C. to
Johannesburg (with a brief stop-over in Dakar) to Windhoek. At that
point (it had been about 30 hours of travel!) we basically crashed
into bed, and woke up the next morning feeling a bit more refreshed.
We picked up our 4-wheel drive truck, which they cancel the insurance
for if they catch you speeding using their satellite navigation
system—so we will be going exactly the speed limit! From there we
headed to the supermarket. After supplying for the next two weeks with
so many groceries, we were off!
Leaving Windhoek, it was immediately apparent that, at least in some
parts of the country, the drought had lifted. The bush was beautifully
green with a lot of new growth. It even down-poured on us for a few
minutes. The drive to NamibRand took us about 6 hours, with stunning
landscapes along the way and the most beautiful dark-red sunset,
complete with billowy clouds. During the drive, we saw ostrich,
baboons, and a large herbivore that none of us knew what it was (we
coined it a Namibian deer for now). (Update: this was a female greater
Kudu.) I wish we could post an awesome photo of the wildlife, but
they were all pretty skittish…hopefully soon.
We arrived in NamibRand in the dark and picked up the keys to our
house. NamibRand has also received a bit of rain recently, so we are
excited to visit the sites today and see how they’ve responded.
Update: The internet here at the reserve is pretty slow, so we will
try to post as much as possible (including pictures). We’ll see how it
goes, and if we can’t post regularly from the reserve, we promise lots
of fairy circle and wildlife photos once we return.
Our primary goal for heading to Namibia in just a few days is to learn how fairy circles are created and maintained. What processes actually create fairy circles remains a highly debated mystery with multiple competing hypotheses, despite years of scientific research. We’ll cover a few of the key scientific possibilities in this post and creation stories for the fairy circles a bit later (so stay tuned)!
These regularly spaced bare circles of ground in arid grasslands have several highly perplexing qualities. The first, and most fascinating to me, is how evenly spaced they are. They have a honeycomb-type pattern that extends for hundreds of miles. This pattern is the result of self-organization–meaning that it isn’t designed but rather arises from the interaction of different parts of the system. Classic self-organization examples include birds flocking together, ant colonies, beehives, or even the creation of human society! All of these classic examples, however, involve individuals with behavioral choices, and these choices tend to be a critical component necessary for self-organization. Fairy circles, though, are the result of individual grasses–so no behavior here. This makes fairy circles a really interesting, and pretty unique, example of a complex system self-organizing.
One hypothesis is that fairy circles might arise from individual plants competing with one another. The Namib desert is an extremely harsh environment with very little rainfall (less than 4 inches a year), so competition between plants is fierce. Specifically, these plants have to compete for precious resources, such as nitrogen, other nutrients, and especially water. So, this intense competition for water and nutrients leads to individuals that win and lose–all within a small area. The individuals that lose die-off, creating a small blank area in the grassland. Rainfall and nutrients in this newly blank soil can then be used by the neighboring individuals, or the ones on the outside of the fairy circles. These individuals then grow larger (a pattern we do, indeed, observe in fairy circles), making them even better competitors. Any seedling that manages to establish in a fairy circle will then very likely be outcompeted by these larger individuals that form the outside of the ring.
Alternatively, a common pattern in the Namib desert are termite nests in the center of fairy circles. So, perhaps termites actually create the circles? Termites act as ecosystem engineers–meaning they are well known for modifying their environments. Termites may eat the vegetation in the middle of the circles, creating the bare spots we see. As termites consume all the vegetation in the center, this produces more moisture in the center of the circle. Similarly to the previous hypothesis, the grasses at the edge of the circles can then access this water to grow larger. Other studies have, indeed, observed termite nests in 80% to 100% of all circles, but it is unclear if the termites are taking advantage of the fairy circles or, rather, creating the fairy circles.
Clearly, the verdict is still out! We are going to be examining fairy circles that have been manipulated to help us distinguish between hypotheses. In 2015, Nichole and her collaborators added water and nutrients to some fairy circles and removed termites from other circles. Now, we have the opportunity to go back and see how the circles have responded to the various treatments, hopefully allowing us to better understand how they are created in the first place. Fingers crossed!