By Don Pinnock – Daily Maverick
From the smallest microbes to the largest mammals, a sweeping new study has painted the clearest picture yet of how human activity is reshaping life on Earth.
Our footprint is everywhere and it’s leaving complex, far-reaching marks on the natural world. We’re not only changing which species exist and where, but are also eroding the variety of life in our local ecosystems.
This is the conclusion of 16 scientists from across Europe who studied more than 2,100 research papers covering more than 100,000 locations around the globe. Their paper has just been published in the journal Nature.
By comparing impacted ecosystems to similar, less-disturbed ones, the team quantified just how much human activity is altering nature.
They grouped the human pressures into five key types: land-use change (like farming and urbanisation), resource exploitation (such as logging or overfishing), pollution, climate change and invasive species. These, they say, overlap and reinforce one another in many ecosystems, intensifying their effects.
Each of these pressures leaves a unique fingerprint on nature. For example, pollution and habitat destruction were found to have the most immediate and damaging impact on the diversity of life in a given area. Climate change and invasive species, while more gradual in their influence, still significantly altered the makeup of ecosystems.
Local losses
One of the most striking findings from the study was how these pressures reduce biodiversity at the local level. On average, places affected by human activity had noticeably fewer species than nearby, more pristine locations. The richness of life – how many different species are present – was consistently lower near humans.
We need to take care of Africa’s amazing biodiversity. (Photo: Don Pinnock)
This local loss matters because it disrupts ecosystem functions. Fewer species can mean less pollination, weaker pest control and more fragile food webs. For communities that rely on healthy ecosystems for agriculture, clean water and resilience to climate shocks, these changes are deeply consequential.
Larger animals like mammals and birds are especially vulnerable to local diversity loss. (Photo: Don Pinnock)
Interestingly, says the study, the effect varies by type of organism. Larger animals like mammals and birds were especially vulnerable to local diversity loss. In contrast, microbes and fungi – organisms that are smaller and reproduce faster – showed higher changes in community composition, but not necessarily in local species richness.
For years, ecologists feared that human activity was making the world’s ecosystems increasingly alike – a concept called “biotic homogenisation.” Imagine grasslands in Africa and Asia slowly filling with the same invasive plants or bird species, crowding out the unique local wildlife. But this study suggests the reality is more nuanced.
Across all the data, there was no clear global trend toward homogenisation. In fact, in many cases, ecosystems became more different from one another, not more similar. This “biotic differentiation” happens when different species respond differently to stressors like pollution or habitat loss, leading to varied changes in community makeup across locations.
However, scale plays a key role. At larger, regional or global scales, ecosystems do tend to become more similar – likely due to the spread of widely adaptable species and human-assisted movement of plants and animals. At smaller, local scales, the opposite is true: stressed ecosystems become less alike, often shaped by random processes like local extinctions or new species colonising a site.
Shifting communities
While homogenisation wasn’t consistent, another trend was: community composition is changing. Almost everywhere they looked, scientists found strong shifts in which species were present, even if the total number didn’t always drop.
For example, when land is cleared for farming or exposed to heavy pollution, some species vanish while others thrive. These winners are usually generalist species – those that can survive in a variety of environments and often benefit from human-altered landscapes. Think of pigeons, rats or weedy plants.
The Namaqualand flower extravaganza is the result of disturbed land. (Photo: Don Pinnock)
The spectacular spring daisy display in Namaqualand occurs because they are pioneer species on disturbed land and thrive from reduced competition. The losers are usually specialists, the ones that need specific conditions to survive, like orchids or large carnivores.
This reshuffling has serious consequences. It can erode the unique identity of ecosystems, reduce their stability and increase the risk of collapse. Some changes happen quickly, within years of a new development or pollution event, while others build up over decades.
What makes this study stand out is its size and scope. The team reviewed data from more than 3,600 independent comparisons covering nearly 100,000 impacted reference sites, looking at ecosystems from every continent and across land, sea and freshwater. They analysed all major types of life, including plants, animals, insects, fungi and microbes.
They also used a standardised method for comparing “impacted” sites (where human activity is present) with “reference” sites (as close as possible to undisturbed). This approach gave them a direct measure of the human effect and allowed them to make meaningful comparisons across vastly different environments.
While many studies have focused on how biodiversity changes over time, this analysis focused on spatial differences, comparing places instead of tracking change at one site. This gave a clearer picture of how human pressures reshape ecosystems in the present, not just over years or decades.
Drivers of change
Pollution and land-use change came out as the most disruptive forces overall. These pressures not only reduce local diversity, but also cause the biggest shifts in which species are found. That’s not surprising. Destroying a forest or dumping pollutants into a river has immediate and visible consequences for the life living there.
Resource exploitation (like fishing, hunting, or logging) also had significant effects, especially when intense. Climate change and invasive species had more varied impacts, depending on the ecosystem and organisms involved.
The study also highlighted that smaller creatures – microbes, fungi, and insects – tend to show faster and more dramatic shifts. Their short life cycles and ability to spread quickly make them more responsive to environmental changes, for better or worse.
Insect populations are greatly diminished. (Photo: Don Pinnock)
Perhaps most revealing is how different aspects of biodiversity change are linked. Places that saw a big drop in local species also tended to show bigger shifts in community composition and more variation from one site to another. In other words, when local diversity collapses, the entire structure of an ecosystem is altered.
This interconnectedness suggests that protecting biodiversity isn’t just about saving individual species. It’s about safeguarding the networks of interactions that keep ecosystems functioning – pollinators and plants, predators and prey, fungi and roots.
Benchmark study
The study’s findings arrive at a crucial time. Governments and organisations around the world have committed to ambitious biodiversity goals, such as protecting 30% of the planet by 2030. But to meet these goals, we need a better understanding of what’s really happening on the ground.
This new research offers a benchmark for measuring progress. It shows where pressures are strongest, which species are most at risk and how different environments respond to human activity. It also challenges some long-held assumptions – like the idea that ecosystems are becoming globally uniform – while reinforcing others, like the huge impact of pollution.
For conservationists, land planners and policymakers, this information is vital. It underscores the need for tailored, local action, not just sweeping global targets. And it highlights the importance of reducing pollution, protecting intact habitats and managing resource use wisely.
This study doesn’t offer a simple message. Biodiversity loss is not happening the same way everywhere. It’s not always a slow fade – it can be a sudden shift. And it doesn’t always mean fewer species overall, it often means different ones.
But one thing is clear: human activity is transforming nature on a massive scale. These transformations affect the health of our food systems, water sources, climate resilience and ultimately our own survival.
The researchers conclude with a call to action: bending the curve of biodiversity loss is one of the greatest challenges we face. Their work offers a crucial roadmap, showing where the damage is happening and what’s needed to reverse it. Whether we act on that knowledge is now up to us.
