Invasive species are already everywhere. Everyone can help stop them.
Across Portugal and Spain, from May 23rd through the 31st, two nations have joined forces to illuminate one of ecology's most overlooked emergencies: the silent conquest of native ecosystems by invasive species. Ranked fifth among global biodiversity threats yet largely unseen by the public, these organisms cost the world over 400 billion dollars annually while reshaping landscapes, waterways, and food systems. Through hundreds of free events, scientists and citizens are being invited into a shared reckoning — one that asks not only what has been lost, but what each person may have unknowingly set in motion.
- A crisis costing $423 billion a year has gone largely unnoticed because its damage unfolds slowly, diffusely, and without a single dramatic moment to anchor public alarm.
- In marine environments the threat is even more acute — invasive species are the second-leading cause of ocean biodiversity loss, outpacing most other pressures in a domain already under siege.
- Researchers warn that ordinary citizens are often unwitting vectors, spreading invasive species through travel, trade, and carelessness without ever realizing the ecological chain reactions they trigger.
- Hundreds of free workshops, guided walks, and restoration events are being deployed across both countries and their islands to transform abstract scientific concern into tangible, local action.
- The campaign, now in its binational fifth year, is pushing to surpass last year's record of 387 activities — a measure of how urgently organizers feel the public conversation needs to accelerate.
For nine days beginning May 23rd, Portugal and Spain are mounting their most ambitious coordinated effort yet to bring a largely invisible ecological crisis into public view. Hundreds of free events — guided walks, workshops, control operations, exhibitions — are unfolding across both countries and their islands, all carrying the same urgent message: invasive species are everywhere, and ordinary people have the power to help stop them.
The scale of the problem is difficult to overstate. Ranked fifth among the greatest threats to global biodiversity, invasive species cost the world roughly 423 billion dollars every year. They arrive from elsewhere, reproduce rapidly, and remake entire ecosystems — degrading agriculture, straining water resources, threatening food security, and compromising public health. Yet most people remain unaware. Elizabete Marchante, of Portugal's Invasive Species Research and Management Network, described the week's core ambition plainly: to make biological invasions stop being an invisible problem. These species are already in cities, on beaches, in rivers and farm fields. They touch daily life directly.
The threat is especially severe at sea. Researcher Paula Chainho explained that while invasive species rank fifth among land-based biodiversity threats, they are the second-leading cause of biodiversity loss in marine ecosystems — a distinction most of the public does not grasp. People often do not realize that their own travel or trade habits may be introducing harmful species into new environments. Closing that awareness gap is precisely what prompted the campaign.
The week has grown steadily since Portugal launched a national version in 2020. Spain joined in 2021, and last year the binational effort produced 387 activities. This edition aims to surpass that record, drawing in universities, municipalities, schools, and local associations alongside ecology networks and European conservation projects. The message threading through all of it is one of agency: prevention is within reach, the damage is not inevitable, and for nine days across two countries, the invisible is being made visible.
For nine days starting May 23rd, Portugal and Spain are mounting their largest coordinated push yet to make people see a crisis that has largely remained invisible. Hundreds of free events—control operations, guided walks, workshops, exhibitions—will unfold across both countries and their islands, all aimed at a single urgent message: invasive species are everywhere, they are causing catastrophic damage, and ordinary people have the power to help stop them.
Invasive species rank as the fifth-greatest threat to global biodiversity on the planet, according to the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services. The economic toll is staggering: they cost the world roughly 423 billion dollars—about 364 billion euros—every single year. These are plants and animals that arrive from elsewhere, reproduce with alarming speed, and then reshape entire ecosystems. They degrade agriculture, drain water resources, threaten food security, and compromise public health. Yet most people do not think about them. They do not see them as a problem. This is the gap the week aims to close.
Elizabete Marchante, speaking for the Portuguese Invasive Species Research and Management Network, put it plainly: the goal is to make biological invasions stop being an invisible problem. Invasive species are already in the cities, on the beaches, in the mountains, in rivers, in farm fields, along roadsides—everywhere. They touch people's daily lives directly. Everyone, she emphasized, can play an active role in preventing and reducing this threat. The week will showcase not just the danger but also solutions: ecological restoration projects, examples of citizens taking action, concrete proof that the problem can be addressed.
The scale of the threat is particularly acute in the ocean. Paula Chainho, a researcher at the Marine Research Network and the Center for Marine and Environmental Sciences at the University of Lisbon, explained that while invasive species rank fifth on land, they are the second-leading cause of biodiversity loss in marine ecosystems. Whether an introduced species becomes invasive depends on the conditions it encounters in its new location. When it does take hold, the damage can be severe. Most of the public does not grasp this. People do not realize they themselves might be the ones causing the harm—through travel, trade, or simple carelessness. This awareness gap is what prompted the campaign.
The week has roots. A national awareness week on invasive species began in Portugal in 2020. In 2021, it expanded to include Spain, becoming a binational effort. Last year brought 387 activities across both countries. The year before, 392. This edition aims to break those records. The coordination involves the Portuguese Ecology Society's invasive species network, the Invasoras.pt platform, two European Life projects focused on the problem, and a specialist group on biological invasions. Universities, municipalities, schools, and local associations are all partners in the effort.
Chaiho stressed that prevention is within reach. Any citizen can take preventive action. The week will teach people how. It will show them that this is not a distant, abstract threat but something unfolding in their own communities, something they can see and influence. For nine days, across two countries, the invisible will become visible.
Notable Quotes
The goal is simple but urgent: make biological invasions stop being an invisible problem. Invasive species are already in cities, on beaches, in mountains, rivers, farm fields, roadsides—everywhere. They affect people's daily lives directly, and everyone can play an active role in prevention and mitigation.— Elizabete Marchante, Portuguese Invasive Species Research and Management Network
On land, invasive species rank fifth as a threat to biodiversity. In the ocean, they are the second-leading cause of biodiversity loss. The public often doesn't realize they themselves might be the ones causing this harm through travel, trade, or carelessness.— Paula Chainho, Marine Research Network and Center for Marine and Environmental Sciences
The Hearth Conversation Another angle on the story
Why does this problem stay invisible for so long, even though it's causing such enormous damage?
Because invasive species don't announce themselves. They're not like a hurricane or a flood. They arrive quietly, spread slowly at first, and by the time people notice them, they're already woven into the landscape. A plant takes over a hillside. A fish outcompetes native ones. It happens at a pace most people don't register.
And the economic cost—423 billion dollars a year—that's real money, real losses. Who bears that?
Farmers do, when invasive plants choke their fields or invasive insects destroy crops. Water authorities do, when invasive species clog pipes or degrade water quality. Fishing communities do, when invasive fish collapse the stocks they depend on. The costs are distributed, which means no single person feels the full weight of it.
So the campaign is trying to make people feel that weight?
Not just feel it—understand their own role in it. That's what Paula Chainho emphasized. People don't realize they might be the vector. A plant brought home from a trip. A fish released from an aquarium. A seed stuck to a shoe. Ordinary actions with extraordinary consequences.
What makes this week different from just publishing a report or running ads?
It's participatory. People aren't being lectured; they're being invited to act. They can join a control operation, walk through a restored ecosystem, see solutions in motion. That changes something in how you understand the problem.
The fact that it's worse in the ocean than on land—why is that?
The ocean is more connected. Currents carry things. Shipping moves species across continents in ballast water. And once something establishes itself in a marine ecosystem, it's nearly impossible to remove. On land, you can at least try to pull out an invasive plant. In the water, you're often just managing the damage.
What happens after May 31st?
The awareness doesn't stop. The networks stay in place. The projects continue. But the week creates a moment—a shared moment across two countries—where the problem becomes impossible to ignore.