Human activities and climate change threaten North Africa’s most important wetland | Sciences

The salinity level in some areas of the lake reached around 40 grams per liter in summer and 30 grams per liter in winter, compared to around 5 grams per liter a few decades ago during the rainy season.

Lake Ichkel, which has a unique ecosystem in northern Tunisia and one of the most important wetlands in the region, is under pressure due to human activities and climate change, but measures to mitigate these effects are still possible in the light of a new scientific study. recently published study.

The study was prepared by an international team of researchers under the supervision of the National Institute of Marine Sciences and Technologies of Tunisia as part of an international research project for the protection of the lake.

Cool lake in winter, salty in summer

Wetlands are important ecosystems with abundant and highly productive habitats that play a distinctive and unique role on a global scale, especially in terms of climate regulation, biodiversity and food security.

These systems are experiencing a reduction in their areas and a deterioration in their environmental status in semi-arid regions, particularly in North Africa, due to human and climatic pressures.

Lake Ichkel is no exception to this rule, although it is one of the most important preserved wetlands in the Mediterranean region and an important wintering site for birds migrating between the African and European continents.

The lake is characterized by a unique hydrological performance which is reflected in the seasonal reversal of water exchange with the neighboring lake of Bizerte, itself connected to the Mediterranean Sea, so that it is cool in winter and salty in summer.

The lake receives fresh water from the rain and the valleys that flow into it in winter, and in summer salt water flows into it from the neighboring lake of Bizerte through the “Tinga” canal which connects them due to the drop quantities of fresh water, says Dr. Laila Al-Basti, professor of marine environment and water resources at Tokyo University of Marine Science and Technology, in an interview with Al Jazeera Net via social media.

Thanks to its high environmental value and excellent hydrological performance, Lake Ishkel and its surroundings are, according to the authors of the study, one of the few sites included since the seventies of the last century under 3 international agreements at the same time, which are the Convention on Biosphere Reserves, the World Heritage Convention and the Convention on Wetlands of International Importance “Ramsar”, in addition to also being ratified as a national park since 1980 .

In the opinion of Dr Al-Basti, “the decrease in the quantities of water flowing from the valleys as a result of the construction of dams, the drought and the significant and tangible increase in temperatures in the Mediterranean basin, as a hotspot of climate change in recent years, has led to an imbalance in the vital balance of the lake.”

model used for the first time

In the new study, recently published on the “Scientific Reports” website, the researchers applied a numerical model used for the first time in the southern Mediterranean to assess the performance of the lake in order to improve its water management.

According to Dr. Bashir Al-Bajawi, researcher at the National Institute of Marine Science and Technology, in an exclusive interview. Al-Jazeera Net by phone.

To ensure the accuracy of the results, data on long-term water variables in the lake were entered, such as rainfall, temperature and salinity, as well as the amounts of water entering and leaving it. come out.

Al-Bajawi, the lead author of the scientific paper, explains the biological balance in the waters of the lake, saying, “The food web inside Lake Ishkel consists of nutrients, phytoplankton, the cycle of nitrogen and phosphorus cycle, and disruption of the balance of these cycles leads to what is called nutritional enrichment.” This process is manifested by the increase in nutrients rich in compounds containing nitrogen and phosphorus, which leads to suffocation of the system and lack of oxygen.

The role of the model, according to Dr Al-Bajjawi, is to “determine the balance of the nitrogen and phosphorus cycles or not, while measuring the proportions of nitrogen and phosphorus – which are nutrients for plankton – in the system”.

High salinity and nitrogen emission

The results of the study showed that the salinity level in some areas of the lake reached around 40 grams per liter in summer and 30 grams per liter in winter, compared to around 5 grams per liter a few decades ago during the rainy season. . This elevation “may lead to changes in the vital system of the lake, and it will also have effects on the living organisms inside, such as grasses, algae and fish,” says Al-Bajjawi.

The model used revealed an imbalance in the cycles of nitrogen and phosphorus inside the lake, which led to the emission of quantities of nitrogen into the air, which indicates the presence of pollution in the lake and that the marine plankton is exposed to the effects of human activity. and climate change.

Nitrogen is also emitted in part as nitrous oxide (two nitrogen atoms with one oxygen atom), a greenhouse gas 300 times greater than carbon dioxide.

Dr. Laila Al-Basti, who participated in the study, confirmed that the phenomenon of emission of this compound has also been observed in many lakes and wetlands around the world subject to similar pressures due to human activities and climatic changes.

Possible solutions – according to the Tunisian researcher – are represented in “the development of a national strategy for the management and protection of wetlands, which includes water management and the reduction of chemical and organic pollution within the framework of the national plan for adaptation to climate variables, and rely on sustainable management and the use of nature to meet the environmental challenges of the lake.”

Dr. Bashir Al-Bajawi concludes that the model used can be an effective tool in the future to manage water and monitor the changes taking place in the lake and the future impacts of each project that will take place in or around the lake. .