Wildlife populations around the world have more than halved in just four decades in the face of unsustainable human consumption, a report has warned.
Mammals, birds, reptiles, amphibians and fish have declined on average by 52% from 1970 to 2010, according to WWF's Living Planet Report, which uses information on 10,380 populations of 3,038 species to see how global wildlife is faring.
Experts from the Zoological Society of London (ZSL), which maintains the database of information on the species, said the figures meant that where in 1970 there was a population of 100 animals, now there were only 50.
For freshwater creatures, the situation is even worse, with population declines of more than three-quarters (76%) in 40 years, the "living planet index" of species shows.
The main threats to wildlife populations are loss or damage to their habitat and exploitation through hunting and fishing, the Living Planet Report said, while climate change is already having an impact on wildlife and is set to increase as a threat.
The situation is worst in low-income countries, where wildlife populations have declined by 58% on average between 1970 and 2010, while the richest countries saw a 10% increase, although those nations have seen significant losses in the more distant past, experts said.
Examples of wildlife that are suffering serious declines include forest elephants in Africa, which are facing habitat loss and poaching for ivory and could become extinct within our lifetime, and marine turtles which have seen an 80% drop in numbers.
In the UK farmland birds have been badly hit by habitat degradation, with major declines in species such as corn buntings, but there is better news for red kites and otters which have seen numbers increase with conservation efforts, experts said.
The Living Planet Report also warned that human activity is outstripping the resources the Earth can provide, cutting down forests too quickly, overfishing and putting out more carbon dioxide than the planet can absorb, leading to climate change.
David Nussbaum, chief executive of WWF-UK, said: "The scale of destruction highlighted in this report should be a wake-up call to us all.
"But next year - when countries of the world are due to come together to agree on a new global climate agreement, as well as a set of sustainable development goals - presents us with a unique opportunity to reverse the trends we see in the Living Planet Report.
"We all - politicians, businesses and people - have an interest, and a responsibility, to act to ensure we protect what we all value: a healthy future for both people and nature."
Professor Ken Norris, director of science at ZSL, said: "The scale of biodiversity loss and damage to the very ecosystems that are essential to our existence is alarming.
"This damage is not inevitable, but a consequence of the way we choose to live. Although the report shows the situation is critical, there is still hope. Protecting nature needs focused conservation action, political will and support from businesses."
He added: "We need to explain to the public that what they do is directly behind the trends we are seeing.
"There is an enormous disconnect between going to the supermarket and putting fuel in your car and the global statistics we're talking about here," he warned.
Mr Nussbaum said consumers could reduce their impact on wildlife by choosing products which were sustainable, for example fish with the Marine Stewardship Council (MSC) and timber with the Forest Stewardship Council (FSC) certifications.
He said people could also look at reducing their meat and dairy consumption, which would be good for their health and the planet, and using public transport when they could.
Professor Jonathan Baillie, director of conservation programmes at ZSL, said people should think about everything they do, from recycling to putting pressure on political and industry leaders, supporting sustainable businesses and getting their children outside to reconnect with nature.
WWF is calling for measures including expanding protected areas, scaling up renewable energy production, and diverting investment from damaging activities, making consumption patterns more sustainable - all the more necessary as the human population grows.
Mike Barrett, director of science and policy at WWF-UK, said: "Clearly a growing population is going to be putting increasing stress on the planet's resources, it's why we're calling now for a change in approach to consume more wisely and waste less."