Restoration is a key element of contemporary environmental management, as damaged or degraded ecosystems are guided towards healthier, more resilient and diverse states. As a result, there is widespread interest and attention given to restoration in scientific, management and policy circles globally, particularly about the outcomes and effectiveness of different restoration initiatives.
New insights into restoration management are emerging from China, where many aquatic ecosystems have been highly altered and degraded in recent decades. A new study published in the journal Water Research suggests that water quality in rivers and lakes across China has improved in recent years as a result of significant investment in environmental restoration and water treatment, funded by the Chinese government.
Rapid economic development since the 1970s across China has caused widespread water quality pressures. In particular, eutrophication as the result of nutrient pollution from households, sewage works, agriculture and industry has been a key cause of deteriorating water quality. Blooms of toxic cyanobacteria are common in severe eutrophication cases, and threaten drinking water supplies and aquatic biodiversity.
In the last two decades, the Chinese government has funded river and lake restoration and the reforestation of catchments and riparian zones across the country (e.g. the Natural Forest Conservation Program), in an effort to buffer pollutants and mitigate eutrophication effects. Parallel these restoration initiatives, significant investments have been made into the establishment of wastewater treatment plants, which reduce the amount of untreated human sewage which reaches aquatic ecosystems.
In order to investigate how these restoration management initiatives have influenced water quality in Chinese rivers and lakes, the researchers, led by Yongqiang Zhou from the Taihu Laboratory for Lake Ecosystem Research of the Chinese Academy of Sciences, collected existing weekly data on dissolved oxygen (DO), chemical oxygen demand (COD), and ammonium (NHþ4 -N) at 145 sites across China between 2006 and 2015. These data were analysed alongside data on land use and land cover, population density and GDP for each site, in order to give an indication of factors influencing water quality.
The researchers found a general improvement in water quality in Chinese water bodies, as shown by decreasing annual mean chemical oxygen demand and decreasing ammonium concentrations alongside increasing dissolved oxygen at the 145 nation-wide monitoring sites. Their analysis suggests that these water quality improvements have occured in recent decades alongside (or perhaps, despite) a parallel growth in GDP in local human populations.
This is attributed to government investments in both aquatic and riparian ecosystem restoration, and in more efficient water treatment plants. However, there is a geographical variation in their findings, as areas in the North China Plain and the Northeast China Plain were found to still have widespread poor water quality, as a result of intensive land use and high population density.
The researchers suggest that their results demonstrate that ongoing economic development does not necessarily need to come at the expense of water quality in rivers and lakes. “This is good news, showing that China is taken strong actions to solve their environmental problems concurrently with a further increase in growth” says Prof. Erik Jeppesen from Aarhus University in Denmark, co-author of the paper and member of the EU MARS consortium. In particular, the authors highlight the importance of effective sewage treatment processes in reducing nutrient pollution pressures.
The study, however, is based on water quality data, and as such is likely to (at least partially) obscure the environmental impacts of other pressures such as dam construction, water abstraction and flow modifications, and the introduction of invasive species. In particular, dam construction for hydroelectric production has been widespread across China in the late 20th century, perhaps most notably of the Three Gorges Dam on the Yangtze River, (former) home of the presumed-extinct Baiji.
Whilst the improvements to water quality highlighted in this study are encouraging, river and lakes across China are still subject to multiple pressures impacting their ecological health and diversity. “The increasing use of fertilizers in agriculture and damming of rivers should be of particular concern”, warns Erik Jeppesen.