In fact, we depend on them to sustain agriculture and livestock farming. To enjoy nature and a multitude of services and leisure activities. They represent, without a doubt, one of the great riches of our heritage. Moreover, if we look at their biodiversity, rivers, lakes and reservoirs are home to a very rich fauna and flora, which, sometimes, is also unique to each place. All this despite the fact that rivers and lakes account for no more than 1% of the Earth's land area. A minimal extension that sustains many species that come to the lakes and rivers to drink, and that make them essential ecosystems for life.

At the same time, rivers have traditionally been heavily punished by our activity. We have treated them as if they were an inexhaustible water resource and as collectors of our filth. But water bodies have shown themselves to be sensitive to these impacts. Some places have become real dumps, and sometimes they have been exploited to the point of exhaustion. In fact, all programs of study agree that inland waters are the most threatened ecosystems on the planet.

Aware of this, in 2000 the European Commission published the Water Directive framework . This rules and regulations has obliged all member countries to comply with minimum conditions for the ecological quality of rivers, lakes and reservoirs. As a result, since 2000, effort and money have been invested in improving the quality of inland waters. And the results have been very favorable in general terms. Many river basins have regained the good ecological status they had lost, although there are still "black spots" to be resolved. In this sense, one of the great ecological problems of our rivers is caused by the impact of dams and the fragmentation they generate. issue This problem is exacerbated by the fact that Spain has the largest number of dams per square kilometer in the world - more than 1,000 large and medium-sized dams (with a capacity of more than one cubic hectometer) and thousands of small dams and weirs.

In the case of Navarra, the rivers are in a more than acceptable ecological state. In general terms, their health is good, as can be seen from the reports on this aspect published on the website of the Government of Navarre. In fact, according to the same source, this year the best values for the ecological quality indicators of the historical series have been reached in the region. Undoubtedly, we have made great progress in the quality of the river basins, but this does not mean that Navarre also has bodies of water in a very improvable ecological status .

Another major threat to our river and lake landscapes is the growing presence of invasive alien species. The zebra mussel, one of the best known, continues to represent a serious threat to our ecosystems (it should be noted that one individual of this species can produce more than a million eggs during its lifetime). A few larvae of the species need only survive to colonize all submerged surfaces given the right environmental conditions. And as is almost always the case, the costs of an environmental problem end up being economic costs as well. And as test, a button: in the period between 2005 and 2009 the costs associated with the expansion of the zebra mussel in the Ebro basin have reached 11.6 million euros.

This reality has shadows but also lights, coming from the improvements generated in recent years in the conservation and care of inland waters. However, the relevance of freshwater aquaculture ecosystems requires the attention and care of everyone: from the Administration and Governments -through investment in resources and efforts and making decisions with the best possible criteria-, to scientists and citizens themselves, who can and should report the presence of an invasive species of fish in their neighborhood lake, for example.