Life started in the water, more precisely in the ancient Ocean, more than 3.5 billion years ago, and life on earth is still nowadays completely dependent on water. Humans are more water than anything else, averaging 60-70% of it, so we are also water creatures, but much less compared to plants.
Although we may be led to the idea that there is plenty of water in our planet, most of it is salt water, so we cannot use it directly for its most common uses (drinking, washing, irrigation). In fact, about 97.5% of the water is salt water and 2.5% is freshwater, and most of this, around 70%, is caught in its frozen state in glaciers and in the poles. For one side this is good because if all the water melted we would have a rise of the sea level that would submerge most of the large coastal cities, and extinguish many small island nations such as Maldives, Marshall islands, Tuvalu and Nauru among others, but on the other side it calls our attention to the scarcity of this freshwater resource. So, the climate change may have a drastic effect all over the planet due to rising of the sea level but also due to the increase of deserted areas.
We also know that water circulates all over our planet Earth, evaporating from the Ocean and being deposited in land by rain and snow and then flowing back to the Ocean. This water cycle is being disrupted because of the climate changes and will create more desert areas in the now know temperate zones, causing serve impacts in the ecosystems but also in the human populations that live there.
The impact of climate change will not be only quantitative but also qualitative, meaning that the communities that live in the water will face dramatic changes in terms of their composition and numbers. The warming up of the continental and marine ecosystems will led to a drift of species from tropical areas to more temperate ones. This can be seen easily when we refer to water borne diseases or diseases that have vectors that are water-borne. Malaria is one of them, being noted that after malaria was eradicated from Portugal in 1958, due to heavy use of pesticides and an introduced tropical fish species — Gambusia holbrokii, we may be facing this problem again. The mosquito vectors responsible for the transmission of the parasite Plasmodium have being traced in Madeira Islands and more recently in Alentejo, in Alqueva reservoir. Warmer water makes more probable the dispersion of the mosquitoes and of the parasites.
In fact, the lower we go in the trophic chains, the faster global warming effects can be show in aquatic systems. Microalgae and microorganisms such as bacteria are good examples. Microorganisms respond quicker to changes in environmental conditions such as increase in water temperature and in chemical loads. Larger organisms such as animals can better withstand changes in temperature before a major impact in their populations can be seen.
One or two degrees of increase in water temperature may cause bacteria and microalgae to grow much faster causing blooms – population explosions that may have impacts in the water quality. If this is combined with increases in nitrogen and phosphorus levels – leading to what we call eutrophication that we can have massive algal blooms that can have severe impacts in the water quality and in their uses. Eutrophication is more clearly seen in freshwaters (rivers, lakes, reservoirs) since the smaller volume of water can be more severely impacted by urban or industrial effluents, agricultural runoff with fertilizers and runoff of water in recently burned areas.
In the sea, eutrophication occurs mostly in coastal areas by the same reason stated before, since in the open ocean the dilution may decrease significantly the nutrient load. In freshwaters the main consequence of eutrophication is the occurrence of blooms of cyanobacteria
figure 1 – Tâmega River in Chaves showing a bloom of cyanobacteria.
Water becomes green as pea soup and the heavy populations of cyanobacteria may cause heavy mortality of fish and bird communities due to toxins they produce or due to deoxigenation after their decomposition. The presence of toxins may also compromise the use of the water for recreation, drinking, fishing and aquaculture as well as for agricultural uses. The global warming may increase the occurrence and intensity of these cyanobacteria blooms and also increases the possibility of occurrence of tropical cyanobacteria species in temperate areas. In Portugal, we have the example of Cylindrospermopsis raciborskii, a cyanobacteria more common in tropical areas, that has started to occur in Alentejo reservoirs a decade ago, and now can be seen in lakes and reservoirs of north Portugal.
This impact of the climate change in the water quality can also be seen in costal and marine waters by the occurrence of tropical toxin producing species of bacteria and microalgae. In the current century, we have reports in Portugal of human intoxications due to the consumption of fish and shellfish contaminated with toxins such as tetrodotoxin (produced by a bacteria) and ciguatoxin (produced by a dinoflagelate). These toxins were previously reported only in tropical areas. Now we have them in our colder, but getting warmer, waters. Since these toxins and these organisms are not monitored regularly, because they were not supposed to be here, more intoxications may occur until the legislation is changed.
But we need to take advantage of these changes in microbial aquatic communities and use this enhanced biodiversity to try to mitigate climate change problems. And we are doing that. Cyanobacteria can be isolated, cultured in laboratory and tested for biotechnological application. Recently, we patented one new molecule isolated from a cyanobacterium that can strongly inhibit the malaria parasite Plasmodium. We also protected a molecule, similarly isolated from cyanobacteria, that has strong UV protection, being able to incorporate a novel sunscreen. On the other side, these cyanobacteria may produce exopolysaccharides – EPS – sugars that are excreted to the culture medium, that can be use to mitigate dried soils and help them to retain more water. Similarly, extracts of the same organisms can be used as biostimulants to increase the growth and yield of plants using natural substances.
The reduction of the use of chemical fertilizers and pesticides and the increased use of natural products that can biostimulate plants and at the same time can protect them against plagues is a green strategy that is increasing all over the world. Research is being conducted in research centers like CIIMAR and the development of new spin offs and the inclusion of this technology in large industries is a reality that can make agriculture and wine production greener and safer.
So, cyanobacteria from one side can harm us if they grow in heavy densities in water with toxin producing strains, but on the other side they can help us to produce in a greener and sustainable way agricultural products.
The impact of climate changes in the water quality and quantity is also focused in many of the United Nations Sustainable Development Goals (SDG). The 2030 Agenda for Sustainable Development, adopted by all United Nations Member States in 2015, provides a shared blueprint for peace and prosperity for people and the planet, now and into the future. At its heart are the 17 Sustainable Development Goals (SDGs), which are an urgent call for action by all countries – developed and developing – in a global partnership. They recognize that ending poverty and other deprivations must go hand-in-hand with strategies that improve health and education, reduce inequality, and spur economic growth – all while tackling climate change and working to preserve our oceans and forests. In fact, although there are two main SDG that refer to water directly – SDG 6– Ensure availability and sustainable management of water and sanitation for all and SDG 14 – Conserve and sustainably use the oceans, seas and marine resources for sustainable development, we should also mention SDG 13 – Take urgent action to combat climate change and its impacts. But changes in water quality and quantify due to climate change also impacts other areas refer in the other SDG what give us the clear idea of how broad social and economical impacts in water due to climate changes.
(figure 2 – SGD 14 – Matosinhos beach viewed from CIIMAR buiding at Leixões Cruise Ship terminal)
Europe is also taking action regarding climate change in special the European Green Deal, a road map that will help EU economy sustainable, turning climate and environmental challenges into opportunities across all policy areas and making the transition just and inclusive for all. This road map has actions that will boost the efficient use of resources by moving to clean, circular economy and also to cut pollution and restore biodiversity. The idea is to make EU climate neutral in 2050. Securing the sustainable use of water remains a key challenge in Europe as well as all over our planet. Clean water is an essential resource for human health, agriculture, energy production, transport and nature. Currently, only 40% of Europe’s surface water bodies achieve good ecological status. In addition, even though EU countries have managed to reduce selected pressures, the status of our marine ecosystems remains critical, both in terms of species and habitats. More efforts are needed to achieve Europe’s freshwater and marine-related environmental targets.
Climate change has a severe impact in terms of quality and quantity of available water in our planet but we should continue to implement measures to mitigate those effects and prevent them. Research and technology transfer should be more entangled together with intense dissemination strategies towards all the publics. Measures to mitigate climate changes should not be implemented by governments only but they should be a priority for each and every one of us. We need to continue to reduce emissions, using public transports, riding bicycles, saving energy at home and in our work, implement the 3R strategy, consume what is produced locally, take actions to save green spaces and yes, also demand governmental bodies for more measures and actions.
Save water, preserve water. We are part of the water cycle.
Director of CIIMAR and Professor at the University of Porto
27 Maio, 2020