In the last 50 years, we have lost more biodiversity than in any other period of human history. Biodiversity loss is the progressive decline in the variety of species, genes and ecosystems that sustain life on Earth — and it is happening at an unprecedented rate.
Anyone who had walked through the fields of the Iberian Peninsula 450 years ago would have encountered a landscape and wildlife very different from what we see today. Did you know that in the 16th century, there were zebra-like creatures in Spain? Or that eels were common in rivers at altitudes of up to 1,000 metres? Biodiversity loss has caused the disappearance of hundreds of species, and the causes are no mystery: they are the direct result of how we produce, consume and occupy the planet.
Why is biodiversity declining?
- Habitat destruction: deforestation and agricultural expansion have eliminated or fragmented more than half of the world's original terrestrial ecosystems.
- Overexploitation: more than 50,000 wild species are overexploited to sustain our way of life, according to IPBES.
- Climate change: it alters temperatures, rainfall and seasons, disrupting the balances on which thousands of species depend.
- Pollution: pesticides, plastics and waste discharge are degrading soils, rivers and oceans at a scale that was unthinkable just a few decades ago.
- Invasive species: spreading through trade and tourism routes, they displace native species from their own territories.
According to the IUCN Red List (2025), 47,187 species are threatened with extinction out of a total of 169,420 assessed — nearly 28% of the total. More than a third of all tree species on the planet are at risk, and the extinction rate shows no sign of slowing: a third of the total increase in recorded extinction risk has occurred since 1994.
What will I learn from this article?
Stories the past tells about nature
Paintings are windows through which we can explore the past. Canvases on which hundreds of artists portray a very different reality from the one in which we live today. Carefully observing artworks from centuries ago, we begin to understand how customs and society have changed, how technology has evolved, and also how the natural environment has been transformed.
Biodiversity decline is not something we can analyze in old paintings, however. We cannot forget that, although artists succeeded in capturing a part of reality, art responds to creative impulses and the aesthetic desire of the person holding the brush.
Could we say that Bosch’s Garden of Earthly Delights is a canvas representative of how the world was in the 16th C? In the painting, we see an impressive bestiary made up of dozens of animals of all kinds. But not all are real. Many are imagined by the artist and others are representations of mythological creatures.
Spain is a curious case: we know the state of biodiversity at that time thanks to the Topographical Surveys. These describe Spanish villages and were compiled from questionnaires that were put to intelligent and interested people of the day. The questions embraced subjects such as population, religion, climate, health, architecture, customs and any other issue that could help chronicle the places that made up the Spanish kingdom. They also included questions about agriculture and natural resources which encouraged those surveyed to describe the vegetation and animals in their area.
“The Topographical Surveys broached subjects including population, religion, climate, health, architecture, customs, agriculture and natural resources”
Now a team of conservation biologists from Doñana–CSIC Biological Station have studied the ecological history highlighted by the Topographical Surveys. Their work, which focused on observing species in Spain in the 16th C., has been published by Ecology magazine.
How biodiversity has changed over 450 years
The species that crop up most in the Topographical Surveys are those that played a principal part in the diet of the time, like rabbits, partridges and hares. Wolves are also mentioned very regularly and, in the reports from the highlands, the Brown Bear and Iberian Lynx are often cited. The study is a window on what is happening planet-wide, in every place with its own particular features.
As for red and roe deer, and boar - key animals for hunting by the privileged classes - they are mentioned by nearby communities as being problematic. According to the survey registries, residents in the Madrid villages of El Pardo and Aranjuez complained of the damage the Royal Hunt was doing to cereal crops.
You could, it seems, make out, on the Southern Plains (la meseta sur) of the country, the last examples of encebros, the wild ass that gave its name to the African zebras and which was the hardiest of the many large European species (megafauna) to become extinct following the last Ice Age. The last mentions of these animals in the surveys correspond to villages in the province of Albacete. One of them tells of how encebras (females of the species) were “ash mares the color of weathered rat skin” which “come down often and destroy the wheat and crops sewn) and “run so fast no man can catch them”.
As for the biodiversity of rivers, the river shrimp is mentioned several times as a common food of the time. Noteworthy is the presence of eels, which, according to the Topographical Surveys, could be found in numerous rivers and up to altitudes of 1,000 meters above sea level. Today, they have disappeared completely from the areas mentioned in these documents.
“Eels could be found in numerous rivers and up to altitudes of 1,000 meters above sea level”
Analyzing the past, so as not to come to regret, what we might lose today
The work of this team of conservation biologists from Doñana–CSIC Biological Station gives us a good-quality freeze-frame of nature at a specific time and place in the 16th C. It also invites us to reflect on how biodiversity changes and how its loss and degradation impact on our lives. A window on what is happening planet-wide, in each place with its particular features.
We over-exploit more than 50,000 wild species to satisfy today’s lifestyle, according to estimates by the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES). The organization has sounded the alarm on the dangers we are facing if we prioritize economic growth at the expense of protecting biodiversity. Moreover, the average abundance of native species in major terrestrial habitats has fallen by at least 20% since 1900.
Tackling the threats wild species and ecosystems face – such as overexploitation and climate change – is essential to arrive at a sustainable planet that can look back one day and not have to regret all the life it has lost.
Source:
- https://doi.org/10.1002/ecy.3783
- https://www.sostenibilidad.com/medio-ambiente/naturaleza-deteriora-velocidad-sin-precedentes
Biodiversity loss refers to the decline in the variety of species, genes and ecosystems that sustain life on Earth. It is not just about the disappearance of striking animals or familiar plants. Biodiversity encompasses everything from the soil microorganisms that allow crops to grow to the pollinators that make the fruit we eat possible. When that web thins, the entire structure supporting ecosystems becomes more fragile.
According to the IUCN Red List (2025), 47,187 species are threatened with extinction out of a total of 169,420 assessed. Nearly 28% of everything we know.
The causes are no mystery: they are the direct result of how we produce, consume and occupy the planet.
Habitat destruction tops the list. Deforestation and agricultural expansion have eliminated or fragmented more than half of the world's original terrestrial ecosystems, leaving thousands of species without the space they need to survive. Compounding this is overexploitation: more than 50,000 wild species are overexploited to sustain our way of life, according to IPBES. Climate change acts as a multiplier, altering temperatures, rainfall and seasons and disrupting balances that took millennia to establish. Pollution from pesticides, plastics and industrial discharge degrades soils, rivers and oceans at a scale that was unthinkable just a few decades ago. And invasive species, spreading through trade and tourism routes, displace native species from their own territories before anyone can react.
Since 1900, the average abundance of native species in major terrestrial habitats has fallen by at least 20% (IPBES). In less than 125 years.
The latest update to the IUCN Red List (2025) records 47,187 species threatened with extinction out of a total of 169,420 assessed. But that figure only reflects what has been possible to study. The Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES) estimates that around one million animal and plant species are at risk of extinction — more than at any other point in human history.
What makes this figure particularly alarming is the pace. A third of the total increase in recorded extinction risk has occurred since 1994. We are not talking about a slow geological process. We are talking about something happening within a single human lifetime.
Lo que hace especialmente preocupante este dato es la velocidad. Un tercio del incremento total de riesgo de extinción registrado se ha producido desde 1994. No estamos hablando de un proceso geológico lento. Estamos hablando de algo que está ocurriendo en el transcurso de una vida humana.
Biodiversity loss is not just an environmental problem. It is a direct threat to the systems that underpin both the economy and human health.
Food security depends on the genetic diversity of crops and the health of pollinators. Water quality depends on the integrity of river and coastal ecosystems. Climate regulation depends on forests and oceans that absorb CO₂. And disease resistance depends, in part, on the microbial biodiversity of soil and the balance between host species and pathogens.
When a species disappears, it does not disappear alone. It takes with it the ecological relationships it maintained with other species. That cascade of effects is what scientists call the loss of ecosystem services, and its global economic impact is estimated at tens of trillions of dollars annually.
To grasp the scale of what we are losing, it sometimes helps to look back. A team of conservation biologists from the Doñana Biological Station–CSIC did so in an unconventional way: by reading the Relaciones Topográficas of the 16th century, the questionnaires with which Philip II mapped the kingdoms of Spain.
What they found paints an unrecognisable landscape. Across the southern plateau, the last encebros still roamed — the wild ass related to African zebras. Eels made their way up rivers at altitudes of over 1,000 metres. The wolf, the brown bear and the Iberian lynx are mentioned matter-of-factly in dozens of localities where today they are history or exception.
That contrast between the 16th century and the present is a snapshot of what is happening across the entire planet. Since 1900, the average abundance of native species in major terrestrial habitats has fallen by at least 20%. And the extinction rate, far from slowing, continues to accelerate.