Few landscapes rival the beauty of China's Jiuzhaigou National Reserve. Located in northern Sichuan Province, the park features snowcapped mountains, deep valleys, and deciduous forests that glow brilliantly in the fall. But the park's most popular attractions are the translucent emerald- and sapphire-hued lakes and lapis-tinted streams that meander through limestone land formations sculpted over time by geological activity.
Jiuzhaigou is China's premier national park, but this UNESCO World Heritage Site was mostly unknown to outsiders before the park opened in 1984. That year, some 30,000 visitors came to experience the park's lakes, streams, and waterfalls. Today, Jiuzhaigou receives an average of 7,000 visitors a day, with over 40,000 visitors a day arriving during peak seasons.
The park's popularity has led some to ask: could the influx of tourists disrupt the fragile relationships between the biological, geological, and hydrological features responsible for the natural beauty that draws visitors to Jiuzhaigou in the first place?
According to environmental biologist Yangdong Pan, the challenge for park managers at Jiuzhaigou is balancing tourism, supporting the park, and the local economy, with conservation efforts designed to promote long-term sustainability.
Professor Pan is a faculty member in Portland State University's Department of Environmental Science and Management. His research focuses on environmental monitoring and freshwater conservation by studying microorganisms such as the algae that live in the lakes and streams of Jiuzhaigou.
Working in collaboration with colleagues from the U.S. and China, Pan is developing tools and methods park managers can use to monitor water quality and identify early warning signs of environmental degradation such as nutrient enrichment (eutrophication) that could change the biological and chemical balance of the park's freshwater ecosystems. According to Pan, eutrophication can trigger system-wide transformations resulting in the extinction of keystone species, the introduction of invasive species, the deterioration of habitat, and the reconfiguration of biodiversity and biogeochemistry.
"Pristine karstic ecosystems such as those found at Jiuzhaigou have very low levels of nutrients like nitrogen and phosphorous in their waterways," Pan said. "The absence of these nutrients inhibits the growth of certain species of algae, which has a lot to do with why the lakes and streams at Jiuzhaigou look the way they do. But if you increase the nutrient level by even the slightest amount, you begin to see changes in the biota that make these waters their home, and as a result, the water quality will change. So if you want to keep the park's waterways in their pristine state, you have to be careful about not introducing nutrients into the ecosystem."
But that is precisely what park managers and scientists like Pan worry is happening. The concern is that the massive crowds that visit Jiuzhaigou each year unwittingly track in nutrients that contaminate the water either by direct contact or by percolating through the porous rocks that form the park's foundation's stunning landscapes. Pollutants, including phosphorous and nitrogen, can hitch a ride into the park on shoes and clothing articles. Other sources of nutrient enrichment include food products brought into the park by visitors and tourism-related waste and waste management. And while the trace levels of nutrients carried in by one person may not threaten the park's expansive freshwater ecosystems, multiply that by 40,000 tourists a day, and you increase the risk of harmful spikes in nutrient levels that may result in irreversible damage to the park's lakes, rivers, and streams.
For park managers, the issue is often reinforced by a lack of resources to identify eutrophication's early warning signs. Consequently, by the time they identify spikes in nutrient levels in the water, it may be too late to halt and reverse the damage.
Pan and his colleagues are working on what may be a simple, cost-effective solution to monitoring the park's water quality for eutrophication. Because the microalgae that live in the waters at Jiuzhaigou and elsewhere have short life cycles and are extremely sensitive to changes in their environment, Pan hypothesizes that subtle changes in the composition of species of microalgae found at pristine sample sites throughout the park might indicate shifts in nutrient levels in the water. And it's possible that those subtle shifts could alert park managers to eutrophication even before spikes could be identified in lab tests. The study is the first systematic analysis of the biota living in the lakes and streams of Jiuzhaigou and the first to consider the relation of those species to the environment and tourism impacts.
"The algae that grow on substrates in the waters at Jiuzhaigou are species that thrive in nutrient-poor environments," Pan said. "By collecting samples and cataloging species we find living in pristine conditions, we can assert that these are the species we'd expect to find in a healthy ecosystem. They're a benchmark for water quality in Jiuzhaigou."
In several recent publications, Pan and his colleagues have demonstrated the sensitivity of algae species collected at Jiuzhaigou to nutrient enrichment in their environments. Further findings suggest the early colonization of more nutrient-dependent species can be identified by color changes on benthic habitats in streams and lakes. While Pan notes that there are no hard conclusions yet, evidence the research team has gathered thus far suggests that the composition of algae living in Jiuzhaigou's waters could serve as an early warning sign for nutrient enrichment. Furthermore, suppose trends in the data indicate a correlation between tourist activity, eutrophication, and changes in the composition of algae species present. In that case, park managers and conservationists could use that information to develop further studies exploring the relationships between tourism and ecosystem degradation in streams and lakes at Jiuzhaigou, leading to the development of interventions designed to mitigate the strain of nutrient loading on the park's freshwater ecosystems.
"The work we're doing in Jiuzhaigou will inform management practices at the park," Pan said. "Park managers can integrate our findings into their decision-making process when they're developing plans to address the challenges created by the dual mandate of operating the park for tourism purposes and working to preserve its pristine environment. And by working with international partners and foreign entities, we can promote the open exchange of practices and ideas, which is critical because efforts to manage our limited water resources are a concern for all countries and governments."