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Climate ChangeFuturePollutionSolutions CRISIS – Viability of Life on Earth

Global Water Crisis: Why the World Urgently Needs Water-Wise Solutions

by Mitota P. OmolereAfrica Global Commons Middle East

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Global Water Crisis: Why the World Urgently Needs Water-Wise Solutions

Water is life. Yet, as the world population mushrooms and climate change intensifies droughts, over 2 billion people still lack access to clean, safe drinking water. By 2030, water scarcity could displace over 700 million people. From deadly diseases to famines, economic collapse to terrorism, the global water crisis threatens to sever the strands holding communities together. This ubiquitous yet unequally distributed resource underscores the precarious interdependence binding all nations and ecosystems and shows the urgent need for bold collective action to promote global water security and avert the humanitarian, health, economic, and political catastrophes that unchecked water stress promises.

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The global water crisis refers to the scarcity of usable and accessible water resources across the world. Currently, nearly 703 million people lack access to water – approximately 1 in 10 people on the planet – and over 2 billion do not have safe drinking water services. The United Nations predicts that by 2025, 1.8 billion people will be living in countries or regions with absolute water scarcity. With the existing climate change scenario, almost half the world’s population will be living in areas of high water stress by 2030. In addition, water scarcity in some arid and semi-arid places will displace between 24 million and 700 million people. By 2030, water scarcity could displace over 700 million people.

In Africa alone, as many as 25 African countries are expected to suffer from a greater combination of increased water scarcity and water stress by 2025. Sub-Saharan regions are experiencing the worst of the crisis, with only 22-34% of populations in at least eight sub-Saharan countries having access to safe water.

Water security, or reliable access to adequate quantities of acceptable quality water for health, livelihoods, ecosystems, and production has become an urgent issue worldwide.

This crisis has far-reaching implications for global health, food security, education, economics, and politics. As water resources dwindle, conflicts and humanitarian issues over access to clean water will likely increase. Climate change also exacerbates water scarcity in many parts of the world. Addressing this complex and multifaceted crisis requires understanding its causes, impacts, and potential solutions across countries and communities.

You might also like: Why Global Food Security Matters in 2024

The Global Water Crisis

The global water crisis stems from a confluence of factors, including growing populations, increased water consumption, poor resource management, climate change, pollution, and lack of access due to poverty and inequality.

The world population has tripled over the last 70 years, leading to greater demand for finite freshwater resources. Agricultural, industrial, and domestic water usage have depleted groundwater in many regions faster than it can be replenished. Agriculture alone accounts for nearly 70% of global water withdrawals, often utilizing outdated irrigation systems and water-intensive crops.Climate change has significantly reduced renewable water resources in many parts of the world. Glaciers are melting, rainfall patterns have shifted, droughts and floods have intensified, and temperatures are on the rise, further exacerbating the crisis.

Baseline water stress measures the ratio of total water withdrawals to available renewable water supplies. Higher values indicate m
Baseline water stress measures the ratio of total water withdrawals to available renewable water supplies. Image: United Nations (2019).

In many less developed nations, lack of infrastructure, corruption, and inequality leave large populations without reliable access to clean water. Women and children often bear the burden of travelling distances to fetch water for households. Contamination from human waste, industrial activities, and agricultural runoff also threaten water quality and safety.

Water scarcity poses risks to health, sanitation, food production, energy generation, economic growth, and political stability worldwide. Conflicts over shared water resources are likely to intensify without concerted global action.

Case Study: Water Crisis in Gaza

The water crisis in Gaza represents one of the most severe cases of water scarcity worldwide. The small Palestinian territory relies almost entirely on the underlying coastal aquifer as its source of freshwater. However, years of excessive pumping far exceed natural recharge rates. According to the UN, 97% groundwater does not meet World Health Organization (WHO) standards for human consumption due to high salinity and nitrate levels.

The pollution of Gaza’s sole freshwater source stems from multiple factors. Rapid population growth contaminated agricultural runoff, inadequate wastewater treatment, and saltwater intrusion due to over-extraction have rendered the aquifer unusable.

 In June 2007, following the military takeover of Gaza by Hamas, the Israeli authorities significantly intensified existing movement restrictions, virtually isolating the Gaza Strip from the rest of the occupied Palestinian territory (oPt), and the world. The blockade imposed by Israeli Authority also severely restricts infrastructure development and humanitarian aid.

The water crisis has devastated Gazan agriculture, caused widespread health issues, and crippled economic growth. Many citizens of Gaza have to buy trucked water of dubious quality, as the public network is unsafe and scarce. The United Nations Relief and Works Agency for Palestine Refugees in the Near East (UNRWA) reports that this water can cost up to 20 times more than the public tariff, with some households spending a third of their income or more on water. Long-term solutions require increased water supplies, wastewater reuse, desalination, and better resource management under conflict.

Case Study: Water Shortage in Africa

Africa faces some of the most pressing challenges with water security worldwide. While the continent has substantial resources, poor infrastructure, mismanagement, corruption, lack of cooperation over transboundary waters, droughts, and population pressures all contribute to African water stress.

According to a 2022 report by the WHO and UNICEF’s Joint Monitoring Programme (JMP), 344 million people in sub-Saharan Africa lacked access to safely managed drinking water, and 762 million lacked access to basic sanitation in 2020. WaterAid, a non-governmental organization, explains that water resources are often far from communities due to the expansive nature of the continent, though other factors such as climate change, population growth, poor governance, and lack of infrastructure also play a role. Surface waters such as lakes and rivers evaporate rapidly in the arid and semi-arid regions of Africa, which cover about 45% of the continent’s land area. Many communities rely on limited groundwater and community water points to meet their water needs, but groundwater is not always a reliable or sustainable source, as it can be depleted, contaminated, or inaccessible due to technical or financial constraints. A 2021 study by UNICEF estimated that women and girls in sub-Saharan Africa collectively spend about 37 billion hours a year collecting water, which is equivalent to more than 1 billion hours a day.The 2023 UN World Water Development Report emphasizes the importance of partnerships and cooperation for water, food, energy, health and climate security in Africa, a region with diverse water challenges and opportunities, low water withdrawals per capita, high vulnerability to climate change, and large investment gap for water supply and sanitation.

In the Meatu District in Shinyanga, an administrative region of Tanzania, water most often comes from open holes dug in the sand of dry riverbeds and it is invariably contaminated.
In the Meatu District in Shinyanga, an administrative region of Tanzania, water most often comes from open holes dug in the sand of dry riverbeds and it is invariably contaminated.

Water security in Africa is low and uneven, with various countries facing water scarcity, poor sanitation, and water-related disasters. Transboundary conflicts over shared rivers, such as the Nile, pose additional challenges for water management. 

However, some efforts have been made to improve water security through various interventions, such as community-based initiatives, irrigation development, watershed rehabilitation, water reuse, desalination, and policy reforms. These interventions aim to enhance water availability, quality, efficiency, governance, and resilience in the face of climate change. Water security is essential for achieving sustainable development in Africa, as it affects numerous sectors, such as agriculture, health, energy, and the environment.

Other Countries with Water Shortages

Water scarcity issues plague many other parts of the world beyond Gaza and Africa. Several examples stand out:

India grapples with extensive groundwater depletion, shrinking reservoirs and glaciers, pollution from agriculture and industry, and tensions with Pakistan and China over shared rivers. Monsoons are increasingly erratic with climate change.

India water scarcity
Projections show India will be under severe water stress by the end of the decade. Image: WRI.

Other water-stressed nations include Australia, Spain, Turkey, Iran, Saudi Arabia, and South Africa. 

While the specifics differ, recurrent themes include unsustainable usage, climate change, pollution, lack of infrastructure, mismanagement, poverty, transboundary conflicts, and population growth pressures. But resources often exist; the challenge lies in equitable distribution, cooperation, efficiency, and sustainable practices. Multiple approaches must accommodate local conditions and transboundary disputes.

You might also like: Water Crisis in South Africa: Causes, Effects, And Solutions

Global Water Security Is at Risk

Water scarcity poses a grave threat to global security on multiple fronts. 

First, it can incite conflicts within and between nations over access rights. History contains many examples of water wars, and transboundary disputes increase the risk today in arid regions like the Middle East and North Africa.

Second, water shortages undermine food security. With agriculture consuming the greatest share of water resources, lack of irrigation threatens crops and livestock essential for sustenance and livelihoods. Food price spikes often trigger instability and migrations.

Third, water scarcity fuels public health crises, leading to social disruptions. Contaminated water spreads diseases like cholera and typhoid. Poor sanitation and hygiene due to water limitations also increase illness. The Covid-19 pandemic underscored the essential nature of water access for viral containment.

Finally, water shortages hamper economic growth and worsen poverty. Hydroelectricity, manufacturing, mining, and other water-intensive industries suffer. The World Bank estimates that by 2050, water scarcity could cost some regions 6% of gross domestic product (GDP), entrenching inequality. Climate migration strains nations. Overall, water crises destabilize societies on many levels if left unaddressed.

Solutions and Recommendations

Tackling the global water crisis requires both local and international initiatives across infrastructure, technology, governance, cooperation, education, and funding.

First, upgrading distribution systems, sewage treatment, dams, desalination, watershed restoration, and irrigation methods could improve supply reliability and quality while reducing waste. Community-based projects often succeed by empowering local stakeholders.

Second, emerging technologies like low-cost water quality sensors, affordable desalination, precision agriculture, and recyclable treatment materials could help poorer nations bridge infrastructure gaps. However, funding research and making innovations affordable remains a key obstacle.

Third, better governance through reduced corruption, privatization, metering, pricing incentives, and integrated policy frameworks could improve efficiency. But human rights must be protected by maintaining affordable minimum access.

Fourth, transboundary water-sharing treaties like those for the Nile and Mekong Rivers demonstrate that diplomacy can resolve potential conflicts. But political will is needed, along with climate change adaptation strategies.

Fifth, education and awareness can empower conservation at the individual level. Behaviour change takes time but can significantly reduce household and agricultural usage.

Finally, increased financial aid, public-private partnerships, better lending terms, and innovation prizes may help nations fund projects. Cost-benefit analyses consistently find high returns on water security investments.

In summary, sustainable solutions require combining new technologies, governance reforms, education, cooperation, and creative financing locally and globally. 

Conclusion

The global water crisis threatens the well-being of billions of people and the stability of nations worldwide. Key drivers include unsustainable usage, climate change, pollution, lack of infrastructure, poverty, weak governance, and transboundary disputes. The multiple impacts span public health, food and energy security, economic growth, and geopolitical conflicts.

While daunting, this crisis also presents opportunities for innovation, cooperation, education, and holistic solutions. With wise policies and investments, water security can be achieved in most regions to support development and peace. But action must be accelerated on both global and community levels before the stresses become overwhelming. Ultimately, our shared human dependence on clean water demands that all stakeholders work in unison to create a water-secure future.

More on the topic: Exploring the Most Efficient Solutions to Water Scarcity

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Global Water Crisis: Why the World Urgently Needs Water-Wise Solutions

Water – at the center of the climate crisis

Photocomposition: a faceut with a drop coming out of it, with a red circle behing the drop.

Climate change is exacerbating both water scarcity and water-related hazards (such as floods and droughts), as rising temperatures disrupt precipitation patterns and the entire water cycle.

Water and climate change are inextricably linked. Climate change affects the world’s water in complex ways. From unpredictable rainfall patterns to shrinking ice sheets, rising sea levels, floods and droughts – most impacts of climate change come down to water.

Climate change is exacerbating both water scarcity and water-related hazards (such as floods and droughts), as rising temperatures disrupt precipitation patterns and the entire water cycle.

Get more facts on climate and water below.
 

Water scarcity
 

  • Over two billion people worldwide don’t have access to safe drinking water today, and roughly half of the world’s population is experiencing severe water scarcity for at least part of the year. These numbers are expected to increase, exacerbated by climate change and population growth.
  • Only 0.5 per cent of water on Earth is useable and available freshwater – and climate change is dangerously affecting that supply. Over the past twenty years, terrestrial water storage – including soil moisture, snow and ice – has dropped at a rate of 1 cm per year, with major ramifications for water security.
  • Melting glaciers, snow and permafrost are affecting humans and ecosystems in mid-to-high latitudes and the high-mountain regions. These changes are already impacting irrigation, hydropower, water supply, and populations depending on ice, snow and permafrost.
  • Climate change is one of the key drivers of the loss and degradation of freshwater ecosystems and the unprecedented decline and extinction of many freshwater-dependent populations, particularly due to land use and pollution.
  • Limiting global warming to 1.5°C compared to 2°C would approximately halve the proportion of the world population expected to suffer water scarcity, although there is considerable variability between regions.
  • Water quality is also affected by climate change, as higher water temperatures and more frequent floods and droughts are projected to exacerbate many forms of water pollution – from sediments to pathogens and pesticides.
  • Climate change, population growth and increasing water scarcity will put pressure on food supply as most of the freshwater used, about 70 per cent on average, is used for agriculture (it takes between 2000 and 5000 liters of water to produce a person’s daily food).

 Photocomposition: a dry tree in a dry soil, with the word drought written in bold big letters at the background.

Water-related hazards
 

  • Climate change has made extreme weather events such as floods and droughts more likely and more severe.
  • Rising global temperatures increase the moisture the atmosphere can hold, resulting in more storms and heavy rains, but paradoxically also more intense dry spells as more water evaporates from the land and global weather patterns change.
  • Annual mean precipitation is increasing in many regions worldwide and decreasing over a smaller area, particularly in the tropics.
  • Climate change has increased the likelihood of extreme precipitation events and the associated increase in the frequency and magnitude of river floods.
  • Climate change has also increased the likelihood or severity of drought events in many parts of the world, causing reduced agricultural yields, drinking water shortages, increased wildfire risk, loss of lives and economic damages.
  • Drought and flood risks, and associated societal damages, are projected to further increase with every degree of global warming.
  • Water-related disasters have dominated the list of disasters over the past 50 years and account for 70 per cent of all deaths related to natural disasters.
  • Since 2000, flood-related disasters have risen by 134 per cent compared with the two previous decades. Most of the flood-related deaths and economic losses were recorded in Asia. The number and duration of droughts also increased by 29 per cent over this same period. Most drought-related deaths occurred in Africa.

 Photocomposition: a house on the left, with a lot of water in the bottom of the image. The word floods is written in big bold white letters at the front of both illustrations.

Water solutions
 

  • Healthy aquatic ecosystems and improved water management can lower greenhouse gas emissions and provide protection against climate hazards.
  • Wetlands such as mangroves, seagrasses, marshes and swamps are highly effective carbon sinks that absorb and store CO2, helping to reduce greenhouse gas emissions.
  • Wetlands also serve as a buffer against extreme weather events. They provide a natural shield against storm surges and absorb excess water and precipitation. Through the plants and microorganisms that they house, wetlands also provide water storage and purification.
  • Early warning systems for floods, droughts and other water-related hazards provide a more than tenfold return on investment and can significantly reduce disaster risk: a 24-hour warning of a coming storm can cut the ensuing damage by 30 per cent.
  • Water supply and sanitation systems that can withstand climate change could save the lives of more than 360,000 infants every year.
  • Climate-smart agriculture using drip irrigation and other means of using water more efficiently can help reduce demand on freshwater supplies.

CLICK HERE FOR MORE INFORMATION

https://www.un.org/en/climatechange/science/climate-issues/water?

Water scarcity

Addressing the growing lack of available water to meet children’s needs.

In Djibouti, water is as precious as it is scarce. Since the drought started in 2007, rainfall has dramatically reduced and water levels in traditional wells have dropped forcing women and children to walk long distances for water.
UNICEF/UN0199521/Noorani

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Even in countries with adequate water resources, water scarcity is not uncommon. Although this may be due to a number of factors — collapsed infrastructure and distribution systems, contamination, conflict, or poor management of water resources — it is clear that climate change, as well as human factors, are increasingly denying children their right to safe water and sanitation.

Water scarcity limits access to safe water for drinking and for practising basic hygiene at home, in schools and in health-care facilities. When water is scarce, sewage systems can fail and the threat of contracting diseases like cholera surges. Scarce water also becomes more expensive.

Water scarcity takes a greater toll on women and children because they are often the ones responsible for collecting it. When water is further away, it requires more time to collect, which often means less time at school. Particularly for girls, a shortage of water in schools impacts student enrolment, attendance and performance. Carrying water long distances is also an enormous physical burden and can expose children to safety risks and exploitation.

Early in the morning, children go to fetch water at the nearest water point, 15 kilometres away from their home in Tchadi village.
UNICEF/UNI315914/Haro Niger, 2020. Early in the morning, children go to the nearest water point to fetch water, 15 kilometres away from their home in Tchadi village.

Key facts

  • Four billion people — almost two thirds of the world’s population —  experience severe water scarcity for at least one month each year.
  • Over two billion people live in countries where water supply is inadequate.
  • Half of the world’s population could be living in areas facing water scarcity by as early as 2025.
  • Some 700 million people could be displaced by intense water scarcity by 2030.
  • By 2040, roughly 1 in 4 children worldwide will be living in areas of extremely high water stress.

UNICEF’s response

As the factors driving water scarcity are complex and vary widely across countries and regions, UNICEF works at multiple levels to introduce context-specific technologies that increase access to safe water and address the impacts of water scarcity. We focus on:

Identifying new water resources: We assess the availability of water resources using various technologies, including remote sensing and geophysical surveys and field investigations.

Improving the efficiency of water resources: We rehabilitate urban water distribution networks and treatment systems to reduce water leakage and contamination, promoting wastewater reuse for agriculture to protect groundwater.

Planning for urban scarcity: We plan for future water needs by identifying available resources to reduce the risk of cities running out of water.

Expanding technologies to ensure climate resilience: We support and develop climate-resilient water sources, including the use of deeper groundwater reserves through solar-powered water networks. We also advance water storage through small-scale retention structures, managed aquifer recharge (where water is pumped into underground reserves to improve its quality), and rainwater harvesting.

Changing behaviours: We work with schools and communities to promote an understanding of the value of water and the importance of its protection, including by supporting environmental clubs in schools.

Planning national water needs: We work with key stakeholders at national and sub-national levels to understand the water requirements for domestic use and for health and sanitation, and advocate to ensure that this is reflected in national planning considerations.

Supporting the WASH sector: We develop technical guidance, manuals and online training programmes for WASH practitioners to improve standards for water access.

CLICK HERE FOR MORE INFORMATION

https://www.unicef.org/wash/water-scarcity?

Extreme floods are slashing global rice yields faster than expected

Flooding is emerging as a silent but powerful destroyer of global rice supplies—and the danger is accelerating.

Source:Stanford UniversitySummary:Scientists discovered that a week of full submergence is enough to kill most rice plants, making flooding a far greater threat than previously understood. Intensifying extreme rainfall events may amplify these losses unless vulnerable regions adopt more resilient rice varieties.Share:

    

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Rising Floods Threaten the World’s Rice
Severe flooding is increasingly damaging global rice yields, slashing production by millions of tons and threatening food security for billions. Credit: Shutterstock

Intense flooding has significantly reduced rice harvests around the world in recent decades, putting at risk the food supply of billions of people who rely on the grain as a dietary staple. Between 1980 and 2015, annual losses averaged about 4.3%, or roughly 18 million tons of rice each year, according to Stanford University research published November 14 in Science Advances.

The researchers found that the damage has grown worse since 2000 as extreme floods have become more common in many of the planet’s main rice-growing regions. They report that climate change is likely to further increase the frequency and severity of these destructive floods in the coming decades.

Droughts, Floods, and a Delicate Balance for Rice

Scientists and farmers have long known that rice yields fall during droughts. The new study adds fresh detail to this picture, estimating that droughts reduced rice yields by an average of 8.1% per year during the 35-year study window. At the same time, the work draws attention to a related but less examined danger from too much water. Rice plants benefit from shallow standing water during early growth, yet prolonged or deep flooding can severely damage or kill the crop.

“While the scientific community has focused on damage to rice yield due to droughts, the impacts of floods have not received enough attention,” said Steven Gorelick, the study’s senior co-author and a professor of Earth system science in the Stanford Doerr School of Sustainability. “Our research documents not only areas where rice yields have suffered due to past flooding, but also where we can anticipate and prepare for this threat in the future.”

What Counts as a ‘Rice-Killing’ Flood

The research team clearly spells out, for the first time, the conditions that turn a flood into a lethal event for rice, said lead study author Zhi Li, who worked on the project as a postdoctoral fellow in Gorelick’s lab at Stanford and recently joined the faculty of the University of Colorado Boulder.

They found that a full week of complete submergence during the plant’s growth cycle is the critical tipping point. “When crops are fully submerged for at least seven days, most rice plants die,” Li said. “By defining ‘rice-killing floods,’ we were able to quantify for the first time how these specific floods are consistently destroying one of the most important staple foods for more than half of the global population.”

How the Researchers Measured Flood and Drought Damage

To estimate how much past droughts and floods have harmed rice production, the scientists combined several lines of evidence. They drew on information about rice growth stages, annual global rice yields, a worldwide database of droughts and floods dating back to 1950, a model of how floods behave across landscapes, and a simulation of soil moisture levels over time in major rice-growing river basins.

Their analysis indicates that, in the coming decades, the most intense week of rainfall in key rice-growing basins around the world could deliver 13% more rain than the average for those regions during the 1980 to 2015 baseline period. This projected increase suggests that rice-killing flood conditions may become more common as the climate continues to warm.

Flood-Resistant Rice Varieties and High-Risk Regions

Wider use of flood-resistant rice varieties could help reduce future losses, especially in the areas that face the highest risk. The study highlights the Sabarmati Basin in India, which experiences the longest rice-killing floods, along with North Korea, Indonesia, China, the Philippines, and Nepal, where the impact of such floods on rice yields has grown the most in recent decades. The greatest total losses have occurred in North Korea, East China, and India’s West Bengal.

The researchers also identified exceptions, such as India’s Pennar Basin, where flooding appears to boost rice yields. They suggest that in these locations, hot and dry conditions may allow standing floodwater to evaporate quickly, reducing long-term damage and sometimes even creating favorable moisture conditions for the crop.

Compounding Climate Stresses on Rice

For Gorelick and Li, the new findings reinforce the need to understand how rice responds not only to floods and droughts, but also to heat waves and cold stress, both individually and when they occur in succession. Earlier research has shown that rapid swings from drought to flood and back again can nearly double rice yield losses compared with single flood or drought events on their own. According to the authors, “How these combined effects can be mitigated remains a major challenge.”

Additional co-authors not mentioned above include Lorenzo Rosa, who is affiliated with the Department of Earth System Science in the Stanford Doerr School of Sustainability and the Department of Global Ecology at the Carnegie Institution for Science. The research was supported by a Dean’s Postdoctoral Fellowship awarded to Li by the Stanford Doerr School of Sustainability.

CLICK HERE FOR MORE INFORMATION

https://www.sciencedaily.com/releases/2025/11/251115095918.htm

A monster seaweed bloom is taking over the Atlantic

Source:Florida Atlantic University

Summary:Sargassum has escaped the Sargasso Sea and exploded across the Atlantic, forming the massive Great Atlantic Sargassum Belt. Fueled by nutrient runoff, Amazon outflows, and climate events, these blooms now reshape ecosystems, economies, and coastlines on a staggering scale.Share:

    

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Monster Seaweed Bloom Taking Over the Atlantic
Sargassum on a beach in Palm Beach County in 2021. Credit: Brian Lapointe, FAU Harbor Branch

Researchers at Florida Atlantic University’s Harbor Branch Oceanographic Institute have released a landmark review tracing four decades of changes in pelagic sargassum – free-floating brown seaweed that plays a vital role in the Atlantic Ocean ecosystem.

Once thought to be primarily confined to the nutrient-poor waters of the Sargasso Sea, sargassum is now recognized as a rapidly growing and widely distributed marine organism, whose expansion across the Atlantic is closely linked to both natural processes and human-induced nutrient enrichment.

The review, published in the journal Harmful Algae, sheds new light on the origins and development of the Great Atlantic Sargassum Belt, a massive recurring bloom of sargassum that stretches across the Atlantic Ocean from the coast of West Africa to the Gulf of America.

Since its first appearance in 2011, this belt has formed nearly every year – except in 2013 – and in May, reached a new record biomass of 37.5 million tons. This does not include the baseline biomass of 7.3 million tons historically estimated in the Sargasso Sea.

By combining historical oceanographic observations, modern satellite imagery, and advanced biogeochemical analyses, this review provides a comprehensive framework for understanding the dramatic changes in sargassum distribution, productivity and nutrient dynamics. It also highlights the broader implications of anthropogenic nutrient enrichment on ocean ecology and the need for coordinated international efforts to monitor and manage the impacts of these massive seaweed blooms.

“Our review takes a deep dive into the changing story of sargassum – how it’s growing, what’s fueling that growth, and why we’re seeing such a dramatic increase in biomass across the North Atlantic,” said Brian Lapointe, Ph.D., lead author and a research professor at FAU Harbor Branch. “By examining shifts in its nutrient composition – particularly nitrogen, phosphorus and carbon – and how those elements vary over time and space, we’re beginning to understand the larger environmental forces at play.”

Early in the review, Lapointe and co-authors Deanna F. Webber, research coordinator; and Rachel Brewton, Ph.D., an assistant research professor, both with FAU Harbor Branch, explain that early oceanographers charted the Sargasso Sea based on surface sightings of sargassum, believing the seaweed thrived in its warm, clear, but nutrient-poor waters. However, this notion created a paradox when mid-20th-century oceanographers described the region as a “biological desert.”

However, recent satellite observations, ocean circulation models, and field studies have resolved this paradox by tracing the seasonal transport of sargassum from nutrient-rich coastal areas, particularly the western Gulf of America, to the open ocean via the Loop Current and Gulf Stream. These findings support early theories by explorers who proposed that Gulf-originating sargassum could feed populations in the Sargasso Sea.

Remote sensing technology played a pivotal role in these discoveries. In 2004 and 2005, satellites captured extensive sargassum windrows – long, narrow lines or bands of floating sargassum – in the western Gulf of America, a region experiencing increased nutrient loads from river systems such as the Mississippi and Atchafalaya.

“These nutrient-rich waters fueled high biomass events along the Gulf Coast, resulting in mass strandings, costly beach cleanups and even the emergency shutdown of a Florida nuclear power plant in 1991,” Lapointe said. “A major focus of our review is the elemental composition of sargassum tissue and how it has changed over time.”

Laboratory experiments and field research dating back to the 1980s confirmed that sargassum grows more quickly and is more productive in nutrient-enriched neritic waters than in the oligotrophic waters of the open ocean. Controlled studies revealed that the two primary species, sargassum natans and sargassum fluitans, can double their biomass in just 11 days under optimal conditions. These studies also established that phosphorus is often the primary limiting nutrient for growth, although nitrogen also plays a critical role.

From the 1980s to the 2020s, the nitrogen content of sargassum increased by more than 50%, while phosphorus content decreased slightly, leading to a sharp rise in the nitrogen-to-phosphorus (N:P) ratio.

“These changes reflect a shift away from natural oceanic nutrient sources like upwelling and vertical mixing, and toward land-based inputs such as agricultural runoff, wastewater discharge and atmospheric deposition,” said Lapointe. “Carbon levels in sargassum also rose, contributing to changes in overall stoichiometry and further highlighting the impact of external nutrient loading on marine primary producers.”

The review also explores how nutrient recycling within sargassum windrows, including excretion by associated marine organisms and microbial breakdown of organic matter, can sustain growth in nutrient-poor environments. This micro-scale recycling is critical in maintaining sargassum populations in parts of the ocean that would otherwise not support high levels of productivity.

Data from sargassum collected near the Amazon River mouth support the hypothesis that nutrient outflows from this major river contribute significantly to the development of the GASB. Variations in sargassum biomass have been linked to flood and drought cycles in the Amazon basin, further connecting land-based nutrient inputs to the open ocean.

The formation of the GASB appears to have been seeded by an extreme atmospheric event – the negative phase of the North Atlantic Oscillation in 2009 to 2010, which may have helped shift surface waters and sargassum from the Sargasso Sea southward into the tropical Atlantic.

However, the researchers caution that there is no direct evidence of this movement. Moreover, genetic and morphological data suggest that some sargassum populations, particularly the dominant S. natans var. wingei, were already present in the tropical Atlantic prior to 2011, indicating that this region may have had an overlooked role in the early development of the GASB.

“The expansion of sargassum isn’t just an ecological curiosity – it has real impacts on coastal communities. The massive blooms can clog beaches, affect fisheries and tourism, and pose health risks,” said Lapointe. “Understanding why sargassum is growing so much is crucial for managing these impacts. Our review helps to connect the dots between land-based nutrient pollution, ocean circulation, and the unprecedented expansion of sargassum across an entire ocean basin.”

This work was funded by the Florida Department of Emergency Management, United States Environmental Protection Agency, South Florida Program Project, and the NOAA Monitoring and Event Response for Harmful Algal Blooms program. Historical studies included within the review were funded by the NASA Ocean Biology and Biogeochemistry Program and Ecological Forecast Program, NOAA RESTORE Science Program, National Science Foundation, “Save Our Seas” Specialty License Plate and discretionary funds, granted through the Harbor Branch Oceanographic Institute Foundation, and a Red Wright Fellowship from the Bermuda Biological Station.

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https://www.sciencedaily.com/releases/2025/08/250830001159.htm