The other side of the DANA: biodiversity and threats to public health
The DANA (Isolated Depression at High Levels), a meteorological phenomenon that has been gaining intensity and frequency in recent years, causing a series of environmental, economic and social problems.
Ecological impacts of the DANA: a hidden threat to biodiversity
When the DANA hits, the immediate consequences are devastating: flash floods, material damage and, in the most serious cases, human losses.
The watersheds that have more urbanized land and less vegetation cover are the most affected. The reason is that the urbanized land acts as a slide for the water, offering almost no friction when moving and, therefore, increasing the impact on human and natural assets. The middle and lower reaches of rivers are usually those that have the most severe impacts because they are also where most of the population is concentrated. But their impact on biodiversity is often ignored. This phenomenon can seriously alter natural habitats, especially wetlands, rivers and coastal areas, which are vital for many species.
The main effects of a DANA on ecosystems are those caused by flooding and severe erosion. In the case of a DANA, the drag of nutrients and sediments from terrestrial ecosystems to the sea is more severe and with it the impacts on receiving ecosystems and human assets.
Pests and diseases: a growing danger
A DANA causes drastic changes in species populations, increasing the risk of pests. In the event of an impact on wild populations, the populations that will recover first will be those with a faster life cycle. These species can often become pests due to the large population growth and the lack of their natural controllers that may have decreased after a DANA, or the DANA may have created new habitats that are easily colonized by these species. For example, the accumulation of stagnant water after heavy rains creates an ideal environment for the proliferation of mosquitoes and other disease-carrying insects. These population explosions can be harmful not only to ecosystems, but also to public health.
One of the most worrying effects of the DANA is the increase in mosquito populations, which can act as disease vectors. According to Tomás Montalvo, Head of the Urban Pest Surveillance and Control Service (SVIPLA), we are not currently in a public health emergency situation. Although there may be an increase in risk if optimal weather conditions for the development of vectors such as the common mosquito (Culex pipiens) and the tiger mosquito (Aedes albopictus) occur. The magnitude of the impact on public health of these agents can be reduced if appropriate management measures are implemented, including coordinated surveillance and control, evaluating interventions and carrying out continuous monitoring.
Another species that is in their sights is the grey rat (Rattus norvegicus). With the excess of rain, the sewage systems have been affected, forcing these rodents to come to the surface and seek refuge in buildings. The presence of rats in inhabited spaces increases the exposure and risk of diseases, such as leptospirosis, an infection that is transmitted through the urine of infected animals.
Recommendations from public health entities
In this context, the State Vector Committee of the Ministry of Health, in which Tomás Montalvo has been working these days, has identified three key lines of action to minimize the risks:
- Communication: It is crucial to inform and raise awareness among citizens about the risks associated with these species. This includes warning about the symptoms of vector-borne diseases and offering preventive advice, as well as keeping the population informed about the measures taken to control these vectors.
- Prevention and protection measures: It is recommended to take extreme hygiene measures, using gloves and masks in case of contact with dead animals and applying repellents to prevent mosquito bites. It is essential to avoid direct contact with animals, especially if their health status is unknown.
- Surveillance and control: Work is being done to centralize pest control, facilitating access to intervention services by the population. In Valencia, an intervention and control team is already being implemented that acts in a coordinated manner to manage these situations quickly and effectively.
The health authorities continue to monitor the situation and adapt interventions according to weather conditions and the results of risk assessments.
The role of biodiversity in minimising impacts: nature-based solutions
To mitigate the negative effects of the DANA on biodiversity and human health, it is crucial to implement strategies based on the conservation and restoration of natural habitats. Wetlands and riparian forests act as well-preserved natural buffers, retaining sediments and nutrients carried by the water, while absorbing excess water and reducing the intensity of flooding.
According to Alberto Maceda Veiga, researcher in biodiversity of urban and agricultural freshwater ecosystems at IRBio, "Over the years, human societies have improved our relationship with river ecosystems, but we still have pending issues." The first he points out is to avoid building in flood channels what urban planning has not taken into account.
The second is to improve the state of conservation of riparian vegetation. Riparian vegetation in good condition buffers the speed of the water and helps retain the nutrients, sediments and pollutants carried by the water. When the riparian forest is degraded and river infrastructures, such as bridges, have insufficient openings for the flow and sediment load of the river, collapses and hydraulic dysfunctions occur. Wetlands act as natural sponges, in this sense, a good network of wetlands would be a life insurance against these extreme phenomena.
These nature-based solutions help mitigate the negative impacts on both human assets and natural ecosystems.
The future: adaptation and urgent climate action
The increasing frequency of DANA and other extreme climate events is a reminder of the urgency of acting against climate change. Extreme climate events have had a direct impact on the proliferation of certain vector and/or reservoir species, with possible impacts on public health, especially in urban and peri-urban environments.
Biodiversity conservation policies must take into account these new scenarios and prepare to respond to the public health challenges that may arise. Raising public awareness of these hidden risks is a necessary first step to foster an integrated and effective response.