Coastal Ecosystems Under Pressure: Climate Change, Urbanization, and the Urgent Need for Regional Collaboration
Around the world, coastlines are being relentlessly reshaped by the dual forces of climate-driven sea-level rise and ever-expanding urban development. Beaches—long considered both ecological treasures and economic lifelines—are now facing unprecedented levels of stress. This growing concern was underscored by Uruguayan marine scientist Omar Defeo, a professor at the University of the Republic (UdelaR), during the opening sessions of FAPESP Day Uruguay held on November 13 in Montevideo. His warnings reflect not only local observations, but also trends being documented across continents: the transformation of beaches from resilient dynamic systems into vulnerable, rapidly eroding zones.
Defeo’s message was stark: nearly half the world’s beaches could disappear by the end of the century. This prediction is not an isolated forecast but the result of a global synthesis of ecological data, climate patterns, and socio-economic pressures. For countries such as Uruguay, Brazil, and Argentina—nations with interconnected Atlantic coastlines—this threat represents not just an environmental crisis, but a shared regional challenge requiring coordinated action.
The Structure of a Coastal Ecosystem: A Delicate Interconnected Network
In his presentation, Defeo explained that coastal ecosystems comprise three fundamental and tightly linked zones: the dune system, the beach face, and the submerged or foreshore region. Each plays a distinct ecological role, and their interdependence forms the backbone of coastal stability.
The dune, or post-beach area, rises above the high-tide line and acts as a natural sand reservoir. Winds transport sand from this dry upper region down toward the surf zone. The beach face, which is alternately exposed and submerged depending on the tide, acts as a transitional region. Finally, the submerged foreshore—stretching from low tide to the point where waves begin to break—is a dynamic environment influenced by currents, wave energy, and sediment flow.
This continuous movement of sediment between zones—a bidirectional exchange driven by wind and wave forces—maintains the equilibrium of the coastal system. Importantly, dunes also serve as natural buffers during storms, absorbing the energy of incoming waves and preventing inland flooding. When dunes are flattened or removed for urban development, the consequences can be catastrophic: coastal homes and infrastructure become far more vulnerable to storm surges and wave attack.
Human Activities Disrupting a Natural Balance
Defeo’s team, in collaboration with Brazilian researchers supported by FAPESP, conducted extensive studies to understand how human actions affect this delicate balance. Their research examined 90 sites across 30 beaches in northern São Paulo, providing one of the most comprehensive regional datasets on coastal biodiversity and ecosystem health.
The findings, published in Marine Pollution Bulletin, revealed that human presence is the most disruptive force, even more than previously assumed. Notably:
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High densities of beachgoers were linked to significantly reduced species richness and biomass, especially in submerged zones.
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Buildings constructed directly on the sand disrupted sediment flow, reducing habitat quality.
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Mechanical beach cleaning, which removes organic matter and alters the sediment profile, further decreased species diversity.
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Despite reduced richness, the abundance of certain organisms increased, particularly opportunistic species such as polychaete worms that flourish in areas with human-derived organic waste.
A striking takeaway from the research is that human impacts are not confined to the area where they occur. Activities on dry sand—construction, foot traffic, pollution—extend their influence into the lower and submerged regions. This demonstrates that coastal ecosystems operate as integrated units: disruptions in one zone inevitably ripple across the entire system.
A Global Perspective: Worsening Erosion on Every Continent
Complementing these regional studies, Defeo led another large-scale investigation published in Frontiers in Marine Science, evaluating 315 beaches worldwide. The results were alarming: one-fifth of these beaches show intense, extreme, or severe erosion. While climate-driven sea-level rise, changes in wind patterns, and altered wave behavior play significant roles, the findings highlight a crucial theme—human activities amplify natural stressors, accelerating erosion and ecosystem degradation.
Certain beach types proved especially vulnerable. Reflective beaches, with their steep slopes and high-energy wave interactions, were found to be highly susceptible to anthropogenic impacts. Intermediate beaches, which combine traits of reflective and dissipative systems, also showed significant erosion in regions with dense human settlement. These insights reinforce the importance of managing coastal development carefully and adapting policy frameworks to local geomorphological characteristics.
Economic, Social, and Environmental Stakes
The loss of beaches is far more than a geographic inconvenience. Coastal ecosystems support:
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Biodiversity, including crustaceans, fish nurseries, and migratory birds
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Local economies, particularly tourism and small-scale fisheries
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Natural defenses that protect inland communities from flooding and storm damage
As beach ecosystems collapse, so too do the services they provide. For coastal nations like those in South America, where tourism and fishing are major economic drivers, the long-term implications are profound. Beach disappearance also raises equity concerns—vulnerable communities often bear the brunt of ecological loss, as they lack the resources for coastal reinforcement or relocation.
Regional Collaboration: A Shared Responsibility for a Shared Coastline
The FAPESP Day Uruguay symposium emphasized the need for scientific and political collaboration across borders. The opening ceremony brought together key figures such as Uruguay’s ANII president Alvaro Brunini, FAPESP scientific director Marcio de Castro, and Brazil’s ambassador to Uruguay, Marcos Leal Raposo Lopes. Their presence highlighted the growing recognition that coastal issues transcend national boundaries.
During the oceanographic sciences session moderated by Marcelo Dottori of the University of São Paulo, contributions from experts such as Cristiana Seixas (UNICAMP) and Natália Venturini (UdelaR) added broader perspectives on coastal governance, conservation, and sustainable development.
Defeo’s call for partnership—particularly between Uruguayan, Brazilian, and Argentine scientists—reflects the realities of shared ecosystems. Marine species, sediment flows, and climatic impacts do not adhere to political borders. Effective conservation therefore requires cooperative monitoring, shared policies, and united research efforts.
Conclusion: A Critical Moment for Action
The accelerated erosion of beaches worldwide is a clear indicator of the pressures human society is exerting on natural systems. The research presented by Omar Defeo and his collaborators provides a compelling evidence base demonstrating that coastal ecosystems are at a tipping point. Without intervention, the consequences will be felt not only in ecological degradation, but also in economic loss, social disruption, and increased vulnerability to climate-driven hazards.
Yet, the situation is not hopeless. Strengthening regional cooperation, limiting uncontrolled coastal urbanization, restoring dune systems, and implementing science-based management plans can still preserve many of these environments. The call to action is urgent and universal: protecting coastlines today is an investment in the environmental resilience, economic stability, and safety of future generations.
Story Source: Fundação de Amparo à Pesquisa do Estado de São Paulo.
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