The drought that especially affects the internal basins of Catalonia is also noticeable in species that are annoying or even harmful to human health, such as some types of mosquitoes. The presence of water is essential for the survival and reproduction of practically all mosquito species that live in regions like ours and, consequently, the lack of rain is a factor that can limit the expansion of these insects.
“If unfortunately the drought continues in the coming months, it is to be expected that in spring and summer we will have fewer mosquitoes of species such as the tiger or the common one, but the issue is more complex than it seems,” explains Roger Eritja, in advance, doctor in entomology and head of entomology and data validation of the Mosquito Alert project.
Carles Aranda, head of the Mosquito Control Service of the Baix Llobregat Regional Council, agrees with the initial diagnosis but in other words: “Logic tells us that the less water, the fewer mosquitoes; but various factors must be taken into account to know whether this year we will have fewer or more of these stinging insects.
The main element for the presence of mosquitoes is water (where these diptera lay their eggs and develop larvae), “but in urban areas water is not only available to mosquitoes due to the rain, they can find it in all types of utensils left outside, buckets, pots or flower vases in cemeteries, to give a few examples,” explains Roger Eritja. Thus, even in a drought emergency, mosquitoes can reproduce if citizens are not careful to avoid leaving water at their disposal, even in small quantities.
Many species of mosquitoes lay their eggs on water (so the presence of the liquid element is essential) but others can deposit them on dry surfaces waiting for rain or any other supply of water to arrive. There are even some mosquitoes that have the ability to detect places where there has been water, for example the edges of buckets, and lay their eggs there, which in the case of the tiger mosquito can survive dry for weeks, explains Roger. Eritja. Another factor in favor of mosquitoes – and to the detriment of humans – is climate change. “The increase in temperatures favors the reproduction of mosquitoes, accelerates the life cycle of these cold-blooded species and, in addition, lengthens the period of the year in which they are active, as we have also seen in Catalonia in recent years,” he concludes. the entomologist.
In the natural environment, in areas such as Baix Llobregat, the management of available water resources, for example that from wastewater treatment plants, also influences the presence of mosquitoes. “Right now we are doing treatments to control the Aedes detritus mosquito, which lives at this time of year in floodplains and near the sea,” details Carles Aranda. “The common mosquito or the tiger can be reduced by drought but if due to lack of rain some people decide to put more buckets to collect water and water gardens, even if it is illegal, in the end it may be that the mosquitoes have even more places to reproduce , we cannot know with certainty,” indicates the person in charge of the Baix Llobregat Mosquito Service.
Carles Aranda and Roger Eritja agree that the data from recent months and years, those affected by the current drought, may have recorded specific decreases in the presence of mosquitoes of some species or in some regions, but there is no data that indicates that a substantial decline in the populations of these stinging insects has occurred or will occur. Neither common mosquitoes nor the invasive species we know as tiger (Aedes albopictus) are going to become extinct this year or in the coming years, experts warn. Control of its expansion, however, is partly in the hands of citizens.
