Written by Larissa Marques Pires-Teixeira
Feature image from John A. Anderson/Shutterstock
Coral reefs are among the most diverse and productive ecosystems on the planet. In addition to hosting thousands of marine species, they support economic activities, protect coastal zones, and provide food for millions of people. However, environmental changes intensified during the Anthropocene, a period characterized by the strong influence of human activities on Earth, are profoundly transforming these ecosystems. Understanding how these changes affect the ecosystem services provided by reefs is essential not only to understand the future of the oceans but also the well-being of human societies that depend on them.
The Anthropocene: when humans became a geological force
Earth’s history is divided into different geological periods, each marked by major changes and defining characteristics. The most recent epoch has been described by scientists as the Anthropocene, and the name itself highlights its defining feature: human influence. Although the proposal to formalize it as an epoch was rejected in 2024, the term continues to be widely used to describe humanity’s profound impact on the planet, as its main characteristic is the increase in multiple anthropogenic pressures. These include climate change, the rapid accumulation of CO₂ and other greenhouse gases, large-scale transformation of Earth’s surface, mainly through agriculture and urbanization, irreversible damage caused by excessive consumption of natural resources, and the pollution of ecosystems worldwide (Crutzen 2016; Crutzen & Stoermer 2021). As a consequence, the structure and functioning of many ecosystems are being profoundly modified, and the planet itself is being altered on a global scale. Coral reefs are among the ecosystems facing the consequences of these environmental changes associated with the Anthropocene.
Although reefs may appear fragile, their origins lie in extraordinarily long natural processes. Historically, reefs have been shaped by long-term geological, climatic and ecological processes (Darwin 1897; Wood 1999). Geological records show that reefs were built over millions of years by biological communities that gradually formed large carbonate structures through the precipitation of calcium carbonate (CaCO₃) (Kleypas et al. 2001). However, current anthropogenic pressures such as climate change, pollution, overfishing and habitat destruction are altering these ecosystems at an unprecedented rate. Among these factors, rising ocean temperatures associated with global warming represent one of the greatest threats to coral reefs (Hughes et al. 2017).
Ecosystem services provided by coral reefs
Biodiversity and ecosystem services are deeply interconnected. More diverse ecosystems tend to maintain important ecological functions such as nutrient cycling, pollination and ecological stability. When biodiversity declines, the capacity of ecosystems to provide these services can also be compromised. This can directly affect human well-being, particularly in regions where communities depend heavily on nature for food, water and environmental protection (Pereira et al. 2024).
Coral reefs provide multiple types of ecosystem services, generally classified into four main categories: provisioning, regulating, supporting and cultural services. Provisioning services include food supply and income generation through activities such as artisanal fisheries and the harvesting of biological resources. Regulating services involve ecological processes that contribute to environmental stability and coastal protection. As supporting services, coral reefs provide habitat and breeding areas for numerous fish and invertebrate species, create diverse ecological niches that allow many organisms to coexist, and promote biodiversity. In addition, reefs offer important cultural services, including recreational, tourism, educational and spiritual values (Woodhead et al. 2018). But what happens when the ecosystems that support these services begin to change?
New ecosystems, new services?
In the Anthropocene, many reefs may become functionally different ecosystems from those observed in the past. These structural changes can profoundly alter the type and magnitude of the ecosystem services they provide. For example, reduced coral cover can decrease habitat structural complexity, affect fish populations and reduce fisheries productivity (Woodhead et al. 2018). Evidence suggests that coral reef fisheries in some tropical Pacific countries may not meet local nutritional needs in the long term due to climate change (Bell et al. 2013; Woodhead et al. 2018).
At the same time, new ecosystem services may emerge. The tropicalization of temperate regions, for example, may benefit local diving tourism and even increase fisheries productivity in some areas. However, it is important to recognize that the arrival of tropical species into temperate ecosystems can also alter ecosystem functioning and potentially affect the services these systems traditionally provided (Vergés et al. 2019; Woodhead et al. 2018). In other words, new ecosystem services may appear, but they often come with ecological trade-offs.
Living with change
The reality is that many changes occurring in the Anthropocene are irreversible. Reefs that have experienced the extinction of ecologically important species, massive coral declines, widespread bleaching events and the establishment of invasive species are unlikely to return to their past configurations. This does not necessarily mean that reefs will disappear entirely. Instead, they may persist as different kinds of ecosystems, with altered species compositions and ecological functions.
The key challenge for scientists and policymakers is therefore not only to protect coral reefs, but also to understand how they are changing and how to adapt to these new environmental conditions in the coming decades and centuries. This makes it urgent to identify and maintain the ecosystem functions that are crucial for reef sustainability and to ensure the ecosystem services that highly altered reef systems may still provide to human societies in the future (Pereira et al. 2024; Woodhead et al. 2018).
References
Bell, Johann D., Alexandre Ganachaud, Peter C. Gehrke, et al. 2013. “Mixed Responses of Tropical Pacific Fisheries and Aquaculture to Climate Change.” Nature Climate Change 3 (6): 591–99. https://doi.org/10.1038/nclimate1838.
Crutzen, Paul J. 2016. “Geology of Mankind.” In Paul J. Crutzen: A Pioneer on Atmospheric Chemistry and Climate Change in the Anthropocene, edited by Paul J. Crutzen and Hans Günter Brauch. Springer International Publishing. https://doi.org/10.1007/978-3-319-27460-7_10.
Crutzen, Paul J., and Eugene F. Stoermer. 2021. “The `Anthropocene’ (2000).” In Paul J. Crutzen and the Anthropocene: A New Epoch in Earth’s History, edited by Susanne Benner, Gregor Lax, Paul J. Crutzen, Ulrich Pöschl, Jos Lelieveld, and Hans Günter Brauch. Springer International Publishing. https://doi.org/10.1007/978-3-030-82202-6_2.
Darwin, Charles. 1897. The Structure and Distribution of Coral Reefs. 3rd ed., With an appendix by Prof. T.G. Bonney. D. Appleton and Co.
Hughes, Terry P., Michele L. Barnes, David R. Bellwood, et al. 2017. “Coral Reefs in the Anthropocene.” Nature 546 (7656): 82–90. https://doi.org/10.1038/nature22901.
Kleypas, Joan A., Robert W. Buddemeier, and Jean-Pierre Gattuso. 2001. “The Future of Coral Reefs in an Age of Global Change.” International Journal of Earth Sciences 90 (2): 426–37. https://doi.org/10.1007/s005310000125.
Pereira, Henrique M., Inês S. Martins, Isabel M. D. Rosa, et al. 2024. “Global Trends and Scenarios for Terrestrial Biodiversity and Ecosystem Services from 1900 to 2050.” Science 384 (6694): 458–65. https://doi.org/10.1126/science.adn3441.
Vergés, Adriana, Erin McCosker, Mariana Mayer-Pinto, et al. 2019. “Tropicalisation of Temperate Reefs: Implications for Ecosystem Functions and Management Actions.” Functional Ecology 33 (6): 1000–1013. https://doi.org/10.1111/1365-2435.13310.
Wood, Rachel. 1999. Reef Evolution. Oxford University Press.
Woodhead, Anna J., Christina C. Hicks, Albert V. Norström, Gareth J. Williams, and Nicholas A. J. Graham. 2019. “Coral Reef Ecosystem Services in the Anthropocene.” Functional Ecology 33 (6): 1023–34. https://doi.org/10.1111/1365-2435.13331.
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