Of course scientists are people, too! And the reverse is also true — ordinary people can do science. Citizen science, that is.

Citizen science — people helping scientists collect data on a big scale the scientists couldn’t access themselves — is hot. We’re talking the Christmas Bird Count held yearly by the National Audubon Society. A survey of 750,000 banded snails to find out how they’re evolved over the last 40 years due to climate change. A web-based weather monitoring effort for Arizona called Rainlog. (Lots more examples at scienceforcitizens.net.)

The Nature Conservancy’s a leader in citizen science — our volunteers are doing everything from monitoring horseshoe crabs on the shores of the Atlantic Ocean to tracing (on foot, on horseback, by ATV) how far Arizona’s San Pedro River reaches across the land every third weekend in June, at the height of that state’s dry summer season…when it’s scorching hot. (At least they start at 6AM.)

But where does all that data lead? Conservancy scientists Dale Turner and Holly Richter have just published a paper in the journal Environmental Management on just what those dozens of volunteers have found over the last 11 years in the Arizona sun — and how it’s helping protect the San Pedro (a critical habitat for migratory birds) and boost its PR, too. I chatted with Turner to find out more. (Also, see more info about Arizona’s three major river systems and how the Conservancy is helping protect them.)


The San Pedro is a perennial river — which means it has a channel in which it’s always flowing, but then the river also flows out of that and is wet on the land outside of the channel in certain areas for certain periods of the year…is that about right?

DALE TURNER: Yes, it has a defined channel that has a continuous flow. The San Pedro is a small river, so that perennial flow might be very small. In the middle of summer, the perennial flow is something you can often jump across without getting your feet wet. But at flood stage, it can be a fairly large river, fairly violent, takes trees and houses and cars and things like that.

But even though it can flood, the San Pedro is still threatened, right?

TURNER: Yes. It’s primarily a groundwater-driven system, and its persistence is highly threatened by groundwater extraction from neighboring cities and agriculture. The river has lost 50 percent of its original perennial length.

Which is bad news for the wildlife that depend on the river. So is that how this citizen science effort started — because you wanted to measure its “perennial length” outside of the channel, not just its flow in the channel?

TURNER: Right. The three gages [measuring devices] in the San Pedro Riparian National Conservation Area had been indicating that the river’s rate of flow was decreasing for the same season of the year over time, so there was concern that the river was drying up. But the only way to know if the perennial length was changing over time was to do a longitudinal survey that mapped how long it was flowing on the surface at the same time each year.

So how did you recruit over 100 people to go out into the desert at 6am the third weekend in June and walk (in some cases) four or five miles to help you?

TURNER: Let me preface this by saying that, when my colleague Holly Richter started this effort, there was some debate within the community of Sierra Vista, the largest town along the San Pedro River, as to the viability of the river. Some people thought that it was just fine, there was lots of water, there wasn’t a problem. Other people thought it’s basically dead, it’s mostly dry, there’s nothing left. So gathering some data about what was actually there was in part to answer that wide divergence of opinions.

Once the recognition came that we needed some measure of how much of surface flow was left, it was obvious that we needed a lot of people on one day. Volunteers were pretty much the only way to achieve that. What we discovered in the process was that it’s also a great way to reconnect people with their river.

Really? How?

TURNER: It has become a community event. You get Bureau of Land Management staff and Nature Conservancy staff and local landowners, local politicians, scientists, hunters, just the whole gamut of society who have some interest in the river, all down there on the same day getting their feet wet. When we started, we were covering an 80‑kilometer reach of the San Pedro. Last summer, we covered 212 kilometers, along with probably another 100 kilometers of tributary channels. So the project has grown dramatically.

The third weekend in June — that’s when the river’s flow is at its lowest. Why monitor then?

TURNER: In Southern Arizona, we have a very predictable dry summer and a wet summer. The dry summer, typically April, May, June, temperatures get over 100 degrees most every day, and you can pretty much count on it not raining. So, by measuring at the end of the dry summer season, we’re getting perhaps the best gauge of the groundwater conditions that are supporting the surface flow by getting surface flow at its very lowest point before there is recharge from that summer’s rains.

What are the volunteers looking for?

TURNER: The process and the data they are collecting are fairly simple. They go out with a GPS unit and a map, so they know where they’re at, and a predefined length of the river that they are to walk. They record with the GPS unit and on a data form the starting point and the ending point of every wet reach of the river, so every flowing section gets defined by a point at each end.

So what have they found?

TURNER: The length of permanent surface flow — which length of the river is wetted on the third week of June every year — has overall has been relatively stable. But there’s a lot of reach‑to‑reach variation, which almost certainly represents variation in local groundwater exploitation and possibly local water supply variability, due to groundwater inflows coming from nearby mountains.

Probably the most interesting result has been the one portion that had a significant trend across the 12 years of data. It also happens to be the portion where we in collaboration with several partners have retired a number of parcels of irrigated agriculture that had been pumping groundwater for their farming.

I was going to ask — how does all this inform conservation of the river?

TURNER: It had been our expectation that eliminating those groundwater withdrawals close to the river would translate into more water appearing in the river. That was just a hypothesis, and while a fairly reasonable hypothesis, it’s something that’s difficult to prove, because this is a large and complex system. But we have based a land protection strategy on that hypothesis at a number of places along the San Pedro, and this data is probably the strongest evidence we have of the success of that strategy.

There has also been a lot of interest in the data on the part of other scientists. This is a dataset that would be difficult for most academics or even agencies to gather because it covers such a large area and has been running for so many years. The fact that we’ve been able to organize and maintain this effort over time has made it a really valuable resource.

So, 11 years after you started this effort, are people who live around the river still writing it off?

TURNER: I think there is a greater understanding that this is still a viable system with strong natural values. Because of the surveys, a lot of people have seen firsthand the beauty, the vitality of a functioning riparian ecosystem simply by getting out there and getting their feet wet.

But the surveys have also highlighted the vulnerability of the San Pedro, because when you see the river in June, there is not a lot of water left, and by getting a visceral sense of how little is there and how fragile it is, I think people get a far better understanding of the potential loss and how easily that could happen.

Editor’s note: Learn more about the San Pedro River mapping effort and see the maps the data have generated.

(Image: Holly Richter, the Conservancy’s Upper San Pedro River program director, uses a GPS unit to map a stretch of river, her trusty horse Macky provides the transport. Image credit: Holly Richter/TNC.)


If you believe in the work we’re doing, please lend a hand.


  1. This is the best idea! I have been in a program several years ago in Tennessee called Froglogging. As frogloggers we logged in on paper the frogs we heard, saw & counted during the year & turned in our evaluations. I learned a lot about frogs & biologists got their data. Children can get involved with their friends & parents, older folks can enjoy learning about nature.

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