In its new Living Planet Report, the Zoological Society of London (ZSL) says the global loss of species is even worse than previously thought.

The new report suggests populations have halved in 40 years, as new methodology gives more alarming results than in a report two years ago.

The report says populations of mammals, birds, reptiles, amphibians and fish have declined by an average of 52%.

Populations of freshwater species have suffered an even worse fall of 76%.

Compiling a global average of species decline involves tricky statistics, often comparing disparate data sets – and some critics say the exercise is not statistically valid.

The ZSL team says they have improved their methodology since their last report two years ago – but the results are even more alarming.

The 2014 Living Planet Report suggests wildlife populations have halved in 40 years

Then they estimated that wildlife was down “only” around 30%. Whatever the numbers, it seems clear that wildlife is continuing to be driven out by human activity.

The society’s report, in conjunction with the pressure group WWF, says humans are cutting down trees more quickly than they can re-grow, harvesting more fish than the oceans can re-stock, pumping water from rivers and aquifers faster than rainfall can replenish them, and emitting more carbon than oceans and forests can absorb.

It catalogues areas of severe impact – in Ghana, the lion population in one reserve is down 90% in 40 years.

In West Africa, forest felling has restricted forest elephants to 6-7% of their historic range.

Globally, habitat loss and hunting have reduced tigers from 100,000 a century ago to just 3,000.

In the UK, the government promised to halt wildlife decline – but bird numbers continue to fall.

The index tracks more than 10,000 vertebrate species populations from 1970 to 2010. It reveals a continued decline in these populations. The global trend is not slowing down.

The report shows that the biggest recorded threat to biodiversity comes from the combined impacts of habitat loss and degradation, driven by what WWF calls unsustainable human consumption.

The report notes that the impacts of climate change are becoming of increasing concern – although the effect of climate change on species until now is disputed.

WWF is keen to avoid despair. It points to conservation efforts to save species like:

• A Gorilla Conservation Program in Rwanda, promoting gorilla tourism
• A scheme to incentivize small-scale farmers to move away from slash and burn agriculture in Acre, Brazil
• A project to cut the amount of water withdrawn from the wildlife-rich River Itchen in the UK.

Previously, the Living Planet Index was calculated using the average decline in all of the species populations measured. The new weighted methodology analyses the data to provide what ZSL says is a much more accurate calculation of the collective status of populations in all species and regions.