Winners and losers of biodiversity
The presence of a single species – Homo sapiens – is having a dramatic impact, allowing some to thrive and pushing others to the brink of extinction.
Over millions of years, organisms have colonized every possible environment on our planet. Microbes resistant to extreme temperatures have been found in the coldest parts of the poles and the hottest hot springs. Plants, insects and animals cover the lands and populate the seas. We know of at least 2 million species, but scientists estimate that another 10 million still have not been catalogued.
And they may never be, as the number of species, as well as the size of their populations and genetic diversity, shrinks globally, suffering from the depredations visited by Homo sapiens. The deforestation required for agriculture is a big culprit, as is river management with its canals and dams that divide water networks and prevent fish populations from mixing. Over-exploitation of natural resources and the inexorable expansion of the urban environment also impact biodiversity in a major way.
Two sides of the coin
Then there is climate change. Until recently, fluctuations in global temperatures occurred over thousands of years; they are now taking place in less than a century. Rising sea levels and water temperatures are already harming fish, corals and the rest of the marine ecosystem. Yet at the same time, regions that have suffered from cold temperatures for millennia will be colonized by species that thrive in warmer climes. Can this expansion compensate for the losses?
“Biodiversity evolves very differently at a global or local scale,” says Carlos Romão, project manager of Biodiversity and Ecosystems at the European Environmental Agency, and lead author of the recent report State of Nature in the EU. “The negative impact of human activity will be much lower in Europe than in the Amazon because of the semi-natural environment we live in.” Thanks to the strong human presence over a long period of time, a fair amount of adaptation and co-evolution has occurred already. “Over the last century, no species went globally extinct in Europe, only locally,” he adds. Paradoxically, many species have grown so accustomed to living in a man-made landscape – like traditional grasslands and hayfields – that they now suffer from both the intensification and the abandonment of agriculture.
The ability to adapt to new weather conditions, diet and habitat is not evenly distributed. Arctic and alpine species are particularly vulnerable. Moving to a new location can be an option, but two factors are crucial: life cycle – short-lived species are more adaptive than long-lived ones – and dispersal speed. “As you can imagine, flying is the best way to conquer new territories,” explains Romão. “Birds are good at it. It is much harder for amphibians and reptiles, not to mention plants.”
On a more positive note, Romão points out that “when there is action and management, you can reverse trends. It’s called conservation.” Some efforts have produced encouraging results, sometimes bringing back species that were on the brink of extinction. Although they may not always be welcome, some species benefit from human activity. Following trade routes and settling in friendly environment, invasive species that travel the world aboard ships and planes are slowly conquering new territories.
Victims of a microscopic killer
Salamandra salamandra terrestris
The wet and temperate biotopes where the black and yellow newt lives in Europe are rare but protected. In recent years, the population of Fire Salamander has been mostly stable, but in the Netherlands a catastrophe wiped out 96% of the numbers between 2008 and 2013. After a thorough investigation, scientists identified the killer responsible for this carnage: a microscopic organism that was unknown until then. Appropriately named Batrachochytrium salamandrivorans, the fungus kills the amphibians in as little as a week.
Reintroduced but not genetically diverse
Native to the European Alps, this impressive mountain goat is a regular encounter for hikers. It is hard to believe that the Alpine Ibex nearly went extinct in the 19th century, when hunters reduced the species to about 100 individuals in northern Italy. A successful reintroduction programme allowed numbers to increase continuously until the late 1970s, when strict hunting regulations stabilised the population. But now the herbivorous mammal is also benefiting from global warming. Rising temperatures and melting glaciers mean more grazing pastures and less harsh winter conditions. Unfortunately, only a few dozen individuals from the ancestral population were used in a breeding programme in the Swiss Alps at the beginning of the 20th century. With its low genetic diversity, the species may not be sustainable over the long term.
DDT victims and now urbanites
Pesticides in the food chain hit this noble bird of prey hard in the 1960s. The specific reason was an eggshell-thinning effect of a breakdown metabolite in the pesticide DDT. Following the ban on toxic organochlorine chemicals in agriculture, and with improved protection from persecution and nest robbing, Peregrines have now recovered worldwide. In Europe the population was estimated between 12,000 and 25,000 breeding pairs in 2004 – numbers that seem stable. And with plenty of pigeons to catch, Peregrines now populate most major cities.
Diseased and threatened everywhere
This beautiful butterfly, once common in southern England, disappeared completely from Britain as early as the 1920s. Disease, predation by birds and bad weather have all been accused, but there is no conclusive proof. With butterfly populations now shrinking all over the world – some studies suggest that only 1% of the numbers found only a half century ago remain – the Black-veined White is threatened everywhere in Europe. The main reason is agricultural intensification that leads to uniform grasslands. Where farmland is hard to access and exploit, it is often abandoned for socio-economic reasons, replaced by woodland that is uninhabitable for many insects.
Too beautiful, too fragrant
One of the world’s slowest-growing plants, the Lady’s slipper orchid that blooms in late spring can take 6-10 years before actually producing flowers. Still found in every European country today, it suffered a decline to the point of near-extinction by the end of the 20th century. Because amateurs were over-collecting it for its beauty and fragrance, conservation efforts were necessary to repopulate the humid woodlands and limestone soils in which it thrives. This orchid’s pollination strategy is particularly interesting: the plant traps insects into its flower, forcing them to escape through its reproductive organs, where they collect pollen.
Invasive and extremely resilient
This plant is the archetypical invasive species. Originally from North America, it is now present in Europe, where it first appeared in the late 19th century. Its distribution has expanded dramatically since the 1990s, especially in continental climates in Hungary, northern Italy and France. This is bad news for humans because the Ragweed’s pollen is high in allergens: according to a recent study, the levels could rise fourfold by 2050, largely because of global warming. This invasive plant is extremely resilient, creating a clear need for strategies coordinated on a European level to prevent more people from suffering during the blooming season.
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