Portugal’s kelp forests along the northern coast store significant carbon reserves while facing serious threats from warming ocean temperatures and tropical species invasion.
Portugal’s kelp forests along the northern coastline capture and hold far more carbon than previously thought, marine scientists have discovered. These seaweed ecosystems, thriving in the cold Atlantic waters, are proving to be powerful allies in the fight against climate change. Yet researchers warn that rising ocean temperatures could destroy these vital carbon sinks within decades.
The kelp forests, which blanket more than 5,000 hectares of seafloor, store roughly the same amount of carbon as thousands of acres of terrestrial forests. This finding comes from the first comprehensive study of its kind in Portuguese waters, revealing that these underwater ecosystems account for nearly one-seventh of all marine carbon stored along the country’s coast.
Two types of brown seaweed dominate Portugal’s kelp forests. Both species grow rapidly in the nutrient-rich waters where the Atlantic meets the Portuguese shore. The region represents the southern limit where these cold-water species can survive, making the area particularly vulnerable to warming trends.
Scientists from two leading Portuguese research centers spent years measuring the biomass, growth rates, and carbon content of these kelp beds. Their work revealed something surprising: despite covering a relatively small area compared to global seaweed forests, the Portuguese marine ecosystems punch well above their weight in carbon storage capacity.
These underwater forests do more than trap carbon. They create three-dimensional habitats where hundreds of marine species find food and shelter. Small fish hide among the swaying fronds while larger predators patrol the edges. Local fishing communities have long recognized this connection. Octopus fishers report better catches in areas where Portugal’s kelp forests remain thick and healthy, while diving operators bring tourists to explore these underwater ecosystems.
Until now, Portugal’s marine carbon inventory has only included salt marshes and seagrass beds. Adding kelp forests to the list significantly increases the country’s known blue carbon reserves. Blue carbon refers to the carbon captured by ocean and coastal ecosystems, which often store carbon more efficiently than land-based forests.
The research team estimates these seaweed forests capture approximately one-third of all carbon sequestered each year by Portugal’s marine plant habitats. This makes them crucial players in national efforts to reduce atmospheric carbon dioxide levels. Yet they have remained largely invisible in climate planning and marine conservation strategies.
Climate change poses an immediate threat to these ecosystems. Ocean temperatures along the Portuguese coast have been rising steadily. Warmer waters allow species from southern latitudes to migrate northward, a process scientists refer to as tropicalization. As tropical and subtropical organisms invade, they can outcompete or consume the cold-water kelp species.
The researchers have already detected signs of this ecological shift in Portugal’s kelp forests. If temperatures continue rising at current rates, these underwater forests could retreat further north or disappear entirely. This would eliminate not only a major carbon sink but also the biodiversity that depends on these habitats.
Restoration efforts for damaged kelp forests have shown promise elsewhere. In Norway, scientists successfully replanted kelp in areas where sea urchin grazing had created underwater deserts. Australian researchers have developed techniques to grow kelp from spores in nurseries before transplanting them to degraded reefs. These methods could potentially help restore Portugal’s kelp forests if populations decline.
See also: How Scientists are Restoring Kelp Forests
Policymakers are beginning to recognize kelp and other seaweeds as nature-based climate solutions. Scotland has invested in kelp farming research, exploring whether cultivated seaweed can supplement wild populations while generating carbon credits. Iceland is mapping its kelp resources to include them in national climate accounting. Portugal could adopt similar policies to protect and potentially expand its kelp forests while supporting ocean conservation efforts worldwide.
The study arrives at a critical moment for European marine conservation. New restoration laws require member states to identify and protect valuable ecosystems. Portugal now has clear evidence that its kelp forests deserve priority status in both conservation and climate mitigation programs.
The economic value of these forests extends beyond carbon storage. They support tourism, recreational diving, and commercial fisheries. Healthy kelp forests help protect coastlines from storm damage by breaking up wave energy before it reaches shore. They also filter pollutants and excess nutrients from coastal waters.
The findings challenge the common assumption that terrestrial forests are the only significant natural carbon sinks worth protecting. Marine ecosystems, though less visible, can store carbon in sediments where it remains locked away for centuries. Unlike trees, which release their carbon when they burn or decay on land, seaweed often sinks to the deep ocean floor when it dies. Portugal’s kelp forests demonstrate that effective climate action requires protecting all types of ecosystems, not just those that are easily visible. As nations search for natural climate solutions, underwater forests deserve a place at the table alongside rainforests and wetlands.
