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In the same state as the hydroelectric plants of Belo Monte and Tucuruí, the largest river-sea island on the planet still burns diesel oil brought by boat to have light. Half of the year it turns into a swamp, which drove away traditional agribusiness and made the buffalo, with its wide hooves, the central gear of an economy stuck in backwardness.
Larger than Belgium and nestled at the mouth of the Amazon River, Marajó Island, in Pará, is a giant that Brazil seems to have forgotten. Surrounded by water on all sides and located in the same state that houses some of the largest hydroelectric plants in the country, the largest river-sea island on the planet remains isolated, with low human development indices and, in much of its interior, dependent on energy generated by diesel oil brought by barge.
With about 40.1 thousand square kilometers, almost the size of Switzerland, Marajó Island is larger than many countries and is home to approximately 250,000 inhabitants distributed in about 15 municipalities, with Soure and Salvaterra being the main ones. Despite the abundance of water, vast lands, and direct access to the Atlantic, the archipelago carries some of the worst social indicators in Brazil, a contrast that intrigues those who look at the map and see a territory with so much potential seemingly stuck in time.
How the largest river-sea island in the world was born
It is essentially a colossal accumulation of sediments. Over millions of years, the Amazon River descended from the Andes Mountains carrying billions of tons of earth, sand, and organic matter, and, upon meeting the force of the Atlantic Ocean at its mouth, the current lost speed and deposited all this material at the bottom, forming the island.
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This unique geographical position creates a challenging hydrological environment. The island is surrounded by rivers so wide they seem like seas, and the Marajó Bay, which separates it from Belém, is known for treacherous currents, shifting sandbanks, and sudden storms. It is not a calm river: the ferry crossing from Belém to the port of Camará takes about three to four hours of navigation, and this wall of turbulent water was the first major barrier to isolate Marajó from the modern economy.
The island that becomes a swamp half the year
The western portion is dominated by dense Amazon rainforest, with thick forests and winding rivers, where building any road means facing the high cost of deforestation, landfilling, and maintaining asphalt in a humid environment that rapidly degrades concrete. Meanwhile, the eastern portion is covered by large savanna plains and open fields.
At first glance, these plains would seem ideal for roads and crops, but there is a decisive problem. During the so-called Amazonian winter, a period of several months of intense rains, and with the tide pushing the rivers inward, these extremely flat plains simply sink. For half the year, much of eastern Marajó transforms into a gigantic swamp, dirt roads turn into impassable mud, and many houses need to be built on stilts, which makes heavy industry and traditional agribusiness unfeasible.
The buffalo, the solution imposed by geography
When the flooded geography made common cattle and tractors unfeasible, Marajó Island found its solution in an animal perfectly adapted to the environment: the buffalo. With wide hooves that do not easily sink in the mud, a fondness for water, and the ability to graze on aquatic plants that would leave a common cow hungry, the buffalo became the central cog of the local economy, hosting the largest herd in Brazil, estimated between 600,000 and 700,000 heads, more buffalo than people.
The origin of these animals on the island is surrounded by various versions. The most well-known oral tradition tells that the first buffaloes arrived by chance in the 19th century, after the ship transporting them from India to Guyana shipwrecked, and the survivors swam to the island. Later, the herd was reinforced by imports from the farmers themselves. Regardless of the legend, the buffalo today provides meat, the milk for the famous Marajó cheese, and even serves as a mount, including for the local Military Police.
The trap of exporting only raw materials
Despite the strength of the buffalo and açaí, the economy of Marajó Island faces a classic underdevelopment trap: the island exports low-value raw materials and leaves the greater profit outside. In the case of the buffalo, the meat and calves leave the island, but industrial processing, packaging, and large-scale distribution occur in mainland slaughterhouses, and the high freight cost across the Marajó Bay erodes the local profit margin.
With açaí, one of the island’s flagship products and a commodity that moves billions worldwide, the pattern repeats. The fruit is manually harvested by riverside dwellers under strenuous conditions and sent raw to the ports of Belém or Barcarena, where it is processed, turned into pulp, freeze-dried, and exported. The riverside dweller earns mere cents from the harvest, while the mainland industry and global networks earn the dollars, precisely because the island lacks the infrastructure to process locally.
The energy paradox: surrounded by plants, powered by diesel
Perhaps the most ironic bottleneck of Marajó Island is energy. The island is in Pará, one of Brazil’s largest energy producers, home to colossal hydroelectric plants like Belo Monte and Tucuruí, and even exports electricity to other regions of the country. Yet, Marajó, in the same state, suffers from chronic energy insecurity, a difficult contrast to accept.
The problem is delivering reliable energy to such a large island surrounded by water. Running the wiring across the Marajó Bay required long and expensive underwater cables, a fragile infrastructure that, at the slightest problem, leaves entire municipalities in the dark. To compensate, much of the interior relies on diesel generators, creating the paradox of importing fuel by barge, paying high freight, to generate expensive and unstable energy just a few kilometers from some of the largest dams in the world.
The dormant green power
The combination of all these factors, a river that acts as a barrier, soil that turns into a swamp, punitive freight, and lack of reliable energy, has created a sort of dome around Marajó Island, deterring private capital and limiting public investments to a minimum. The social result is harsh, with a lack of opportunities pushing young people towards exodus or vulnerable situations.
Even so, Marajó is far from being a useless land; it is more of a sleeping giant of the green economy. If logistical and energy bottlenecks were resolved, with more robust cables, adapted solar plants, and subsidized fast ferries, the island would have the potential to be a world reference in high-standard ecological tourism, as well as a treasure for the standing forest biotechnology and for an açaí and cheese industry with locally processed origin certification.
Marajó Island is a portrait of how geography, when ignored, can imprison the potential of an entire region. Brazil built its infrastructure on concrete and asphalt, technologies that the flooded plain of the archipelago rejects, and therefore ended up leaving behind a giant at the mouth of the Amazon. Integrating Marajó into the national wealth involves stopping fighting against geography and starting to think of solutions that float, navigate, and adapt to an island that breathes with the tides.
Did you know the size and challenges of Marajó Island, the largest river-sea island in the world? Do you think Brazil should invest to transform the region into a powerhouse of the green economy, or is the isolation too great? Leave your comment, tell us what you think about the future of Marajó, and share the article with those interested in the Amazon, geography, and regional development.
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