Adopt-a-Stream:
Environmental Education at Las Cruces
(or Changing Students' Attitudes Toward Polluted Rivers)

Adopt-a-Stream is a community-based educational program designed to encourage people to learn about the physical, chemical, biological and environmental conditions of the watersheds in which they live. The identification of the sources of pollution and other causes of environmental deterioration too may be part of this program. In this way, the program gives people a tool for decision making and encourages them to take an active role in protecting the water quality and wildlife associated with the streams. This may help to prevent the detrimental effects on the environment of some types of indus-trial and agricultural practices, land clear-ing and domestic pollution. In many cases, Adopt-a-Stream activities involve the restoration of already disturbed habitats.

Students learning how to do chemical monitoring in the Río Jaba.
Photo by Douglas Parsons, University of Georgia

There are many different ways to implement an Adopt-a-Stream program. It can be as simple as organizing the neighbors to pick up the trash, or as complex as developing a long-term chemical and biological monitoring program in the stream. One of the principal aims is to assess the current water quality and observe the changes occurring through time. The biological assessments require the identification and counting of aquatic insects, fish, prawns, algae and other groups of organisms that might be biological indicators of the water's condition. The presence, or absence, of certain species and the changes in their abundance and diversity, may be related to specific levels of pollution and environmental disturbances. Working with aquatic animals may take months or even years of intense sampling to produce some conclusions, much longer than chemical analyses do. However, the time invested is valid because, once the species' role in the ecosystem is known and the relation between fauna and water quality is understood, it becomes a reliable, precise and affordable technique.

Many of these programs are operating in the USA and other countries, where they are becoming popular. However, they are almost unknown in Costa Rica. The only relevant precedent is a program conducted by the OTS at La Selva Biological Station, in Puerto Viejo de Sarapiquí, Northern Costa Rica.

Willing to implement a similar program in Coto Brus and to make this our main environmental education activity, we contacted some community organizations, governmental functionaries, NGOs and other groups in San Vito. The best and fastest response came from teachers working at the Colegio Humberto Melloni, the local High School. This is a vocational school that emphasizes agricultural training and is more interested in topics such agroecology, environmental conservation and organic agriculture. It has a 62-acre experimental area and training farm. It happens that a small stream goes through this property after coming from the opposite city edge, going downtown and passing by a coffee mill. The teachers are concerned about the pollution and the environmental impacts the stream receives in San Vito and inside the school's farm, too.

Now, the high school students are being trained to sample with portable chemical test kits and to do small insect collections. To help them in understanding the differences between polluted and pristine rivers, we brought them to work in the Río Jaba. The Amigos of the Wilson Botanical Garden who had visited our forest preserve will remember this river as a clean water stream going through the forest. The same measurements were made in the Pavo Creek, already polluted when going behind the School's farm. We expect the contrast motivates the students to learn more about freshwater ecology and the processes involved in rivers' pollution, but most of all, to do something about it. The teachers expect this training eventually to become a graded element of one of the school's courses. Until that time, the students are volunteers in an Adopt-a-Stream Club.

Our main problem is that we do not know which native species of aquatic organisms in Coto Brus may work as indicators of the stream's environmental condition. Very few studies about this subject are made in Costa Rica, and what we do know is mostly extracted from foreign scientific literature. It is necessary to discover the exact relations between local species and water quality. To start, we reviewed many of the course books produced by the OTS during the last five years, which occasionally include a study of the aquatic fauna in the San Vito region. Of course, these studies are very punctual in terms of time and geography as well. However, a compendium of the participants' reports written during their stay in Las Cruces will allow us to make a preliminary biological and chemical comparison of both disturbed and undisturbed streams. Usually, these field practices included the measurement of dissolved oxygen, nitrogen, phosphorus and other substances. Counting of insect larvae, plankton and other biological groups made simultaneously might give an idea about what is going on in the watersheds.

We just started last July and we do not have much data yet. However, the first few samplings already showed a significant difference between the two sites, as can be observed in table 1.

Table 1. Average concentrations in mg/l of some substances and percent of oxygen saturation in the water of two streams, in July-September 1998. The fourth column gives the expected values for the typical, undisturbed tropical streams and with non- deforested basins.

These values mean the Jaba river is quite a clean river, except for nitrates that exist in a concentration larger than expected for a non-polluted river. Further sampling will let us know if this is just an accidental high value, or if there is a disturbance upstream that generates the excess of nutrients. Phosphates and chlorine in the Quebrada Pavo show the typical concentrations of a semi-urban stream with some agricultural fields around. What is really interesting is the very low oxygen content of the water near the school. Whereas rapids and waterfalls make the Jaba River's water a little over-saturated, the Pavo creek is very poor in oxygen. One possible explanation is pollution by organic matter dumped in the river, then bacteria and other micro-organisms consume the oxygen when decomposing the dissolved organic substances. The very high concentration of nitrates might support this hypothesis.

Also, the Jaba river has a much richer aquatic fauna than the Quebrada Pavo. The students found a large number of fishes in four species (two of them endemic to South Costa Rica) and twenty-three species of insect larvae in Las Cruces Preserve. However, only one fish and fourteen insects were caught by the school.

These few data produced an immediate reaction in the students. Some of them admitted they used to escape occasionally from class and go swimming in the nearby stream. Now they are very reluctant to indulge in this particular recreation, and the teachers, of course, will be delighted with this side effect of their study results. The next step, after continuing the sampling over a period of one year, will be to produce a document, a poster or another kind of educational display for the community, whose main goal will be to persuade adults and neighbors to join the program.