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Scientists and government officials meet this week in Paris to finalise a key assessment on humanity's relationship with nature.

The Intergovernmental Panel for Biodiversity and Ecosystem Services, or IPBES, will issue the first report of this type since 2005.

It will detail the past losses and future prospects for nature and humans.

One author says the report will highlight the "social and ecological emergency" the world is now facing.

From Monday some of the world's leading researchers in the field of biodiversity will meet in the French capital to work through the details of their report with representatives from 132 governments.

Their conclusions, known as a Summary for Policymakers, will then be published on 6 May.

"I would say that this is the most comprehensive assessment on the state of nature and humanity's place in it," said Prof Sir Robert Watson, who chairs IPBES.

"It is the first intergovernmental assessment - this is much more powerful in my view, it means that governments are fully involved."

What exactly is biodiversity?

Biodiversity is just a sciencey word for all the amazing variety of life that can be found on Earth, their interactions with each other and with their environments.

Image copyright Getty Images Image caption Pollination is one of the key services that nature provides to humans

It encompasses everything from genes, through individual species such as orang-utans, through communities of creatures and then the whole ecological complexes of which they are part.

The phrase, which originated in the 1980s, is a contraction of the words "biological" and "diversity".

It was more formally defined in the UN's Convention on Biological Diversity signed in 1992 as: "Biological diversity" means the variability among living organisms from all sources including, inter alia, terrestrial, marine and other aquatic ecosystems and the ecological complexes of which they are part: this includes diversity within species, between species and of ecosystems."

Why does biodiversity matter to me?

Well, the air you breathe depends on plants producing oxygen, and without bees to pollinate crops, we wouldn't have so many things to eat.

Biodiversity helps provide and maintain our fresh water, fertile soils, our medicines, a stable climate and gives us places for recreation.

All species are interconnected and often depend on each other. So while fungi help maintain the soils of the forest, these healthy soils help plants to grow, insects then carry pollen from one plant to another, animals can eat the plants, and the forest as a whole provides a home for animals.

Losing one species in this chain may not seem like much but each loss weakens the connections that benefit us all.

Back in the 1980s, conservation researchers Paul and Anne Ehrlich said that species are to ecosystems what rivets are to a plane's wing. Losing one might not be a problem, but each loss adds to the likelihood of a disaster.

So why is this report important?

It matters because it will highlight the shocking losses that have hit the natural world over the past 50 years, and will warn that the future is looking bleak for tens of thousands of species.

It will also highlight the threat to humans if the devastation of nature continues.

More than two billion people rely on wood fuel for energy, while around four billion rely on natural medicines. Some three-quarters of our food crops require pollination by insects.

One of the scientists involved told the BBC that the assessment would underline the fact that the world is now facing both a natural and a human emergency.

"Social and environmental changes are much more connected than we have portrayed them in the past," said Prof Unai Pascual, from the Basque Centre for Climate Change, Spain, who is a lead author on the report.

"This assessment will show these connections are based on robust scientific evidence; The evidence is clearer than ever that the negative impacts on nature that we are pushing translate into detrimental changes in people's wellbeing, and that for an increasing proportion of the population on our planet the emergency is not just an ecological emergency, but it is turning into a social and ecological emergency."

Image copyright Getty Images Image caption Researchers say the loss of nature will have big implications for humans

Surely we've heard all this before?

Much of the research about impacts on individual species, such as on bees and other pollinators, has been published before.

In the global assessment, the research team takes a much broader view of what's been happening to the natural world.

For three years, 150 experts from more than 50 countries have looked at 15,000 sources of information.

One significant way in which this assessment differs from previous publications is that it uses knowledge from people who have been living in and preserving ecosystems for generations.

"We have a systematic strategy to include indigenous and local knowledge," said Prof Sandra Diaz from Cordoba National University in Argentina and a co-ordinating lead author for the report.

"So the evidence of what's going on, the different practices to maintain and enhance diversity will not only come from mainstream science but will also come from the deep knowledge of people who have been managing diversity for a long time around the world. So I think we will have a much richer picture than previous assessments."

The full report, stretching to 1,800 pages, will be published at the same time as the 40-page summary.

What will the assessment say?

The details of the summary will remain under wraps until the scientists and political representatives have agreed every last word.

However, as much of the information has been published in one form or another in previous years, we have a reasonable idea of the key messages.

It will likely warn that we are on the brink of a rapid acceleration of the global rate of loss of species. And it will say the threat these losses pose - and the challenge that presents - is on a par with climate change.

Image copyright Getty Images

It's probable also that it will say that farming, deforestation and our demands for energy are undermining the services we get from nature.

"I want people to know that nature is really important, and we shouldn't destroy it, and it is absolutely essential to food, water and energy security," said Prof Sir Robert Watson.

"I want the public to say that we should not be destroying it and urge their governments to make sure they have the right policies in place and to ask: 'what can I do in my everyday life to be more sustainable?'"

Is all this related to climate change?

Climate change will feature heavily in the assessment and is closely linked to the fate of species.

The scientists at IPBES believe the threat from the loss of nature will be as big a challenge to the world as rising temperatures.

This rise is also playing a key role in the destruction of nature. For example, the range of a much larger number of species will be affected by a rise in global temperatures this century of 2 degrees C than by a rise of 1.5C.

The researchers hope that just as the report from the IPCC woke the world up to the scale of the threat of climate change last Autumn, the IPBES report will do the same for nature.

"If you look at IPCC, they managed to show that climate change was a problem for the whole world," said Prof Sandra Diaz.

"Now, it is a problem that no-one ignores."

Will the scientists tell the governments how to act?

Not exactly. The scientists are meant to avoid being "policy prescriptive", which means they can't tell the governments what to do about the crisis facing the natural world.

Image copyright Getty Images

However, the scale of concern is so great that some researchers feel that the report can't afford to pull its punches.

Sir Robert Watson, who will chair the Paris meeting and the report, says the researchers won't be afraid to tackle sensitive issues.

"We talk about some of the drivers of change, such as economic growth, and population growth, because the more people you have and the wealthier they are the more they consume, and the more pressure that puts on nature. Some might say the issue of population is politically sensitive but we don't avoid it."

While the report will likely highlight the policy choices that governments can make, and the implications of those choices, one key takeaway will be that nature and humanity cannot continue to have a "win-win" situation at our current levels of consumption.

"I think this is going to be one of the main messages; we have to be very mindful that having more of everything is not possible now," said Prof Unai Pascual.

"We have to be much smarter in how we allocate our resources to make sure we have sufficient for everyone.

"We need to understand the trade-offs, because once you lose biodiversity it is difficult to reverse."

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