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I'm spending part of this week at biodiversity school.

Not any ordinary school, mind, but Britain's .

This week it hosts a conference with the somewhat arcane title - which doubles as the triennial conference of the , the umbrella organisation encompassing 103 science academies (like the Royal Society) from around the world.

As at any science conference, the jargon flies around thick and fast; but what's interesting about this one is that beneath the jargon lie some of the simplest and most important questions pertaining to the environment and how humankind should manage it in the future.

The questions include: why does biodiversity matter? And how can we do the best for nature in a world that will soon need to feed, clothe and maintain nine billion people?

On one level, of course, biodiversity matters if we decide it matters - if all humanity, or groups of it, decide it's important to preserve tigers or tunas or turtles and do something about it.

But as the Royal Society's former chairman reminded us, biodiversity conservation is absolutely not just about a handful of iconic species and an emotional response to fin and fur.

Non-charismatic organisms (insects, fungi, bacteria, worms, etc) vastly outnumber those you'd find on a conservation charity's posters; so why do they matter? What is, in fact, the scientific case for preserving them?

Long-running research projects such as the run by and the have given us some answers.

In a nutshell, explained from McGill University in Canada as he distilled the results of such projects for his audience, they show that diversity leads to ecosystems that are highly and robust.

So when two plots of grassland, for example, are grown next to each other and one is allowed to contain more species than the other, it will be more productive; and the productivity rises, apparently, because a greater variety of species brings a greater number of ways in which they can complement each other in terms of what they consume and produce.

The complementarities and the richness apply not only to plants, but to insects and other animals; diversity supports diversity.

Plots endowed with high diversity retain their high productivity if something should affect one of the species they contain; low diversity ones decline. So high diversity is a kind of insurance policy against disease or other impacts.

But there's a problem. Humanity may benefit from intact and therefore productive ecosystems; but we also need to create and maintain quite large areas of low diversity in the form of farms.

And the world's food production is going to have to increase as the human population rises. .

So how do we compromise our need for these low diversity zones with the need that both we and nature have for high diversity?

's group at Cambridge University is developing a strategy that involves plotting the sensitivity of a given species to a given ecological change.

A hypothetical example would be something like this. If you needed to drain an area of wetland to grow crops, the local frogs might be extremely sensitive to that, whereas birds might be fine with a bit of drying so long as some moisture remained.

So as far as the frogs are concerned, the best solution would be patches of intense farming with patches of intact wetland in between. One's good for assuaging human hunger, the other's good for frogs.

But the best strategy for the birds would be to farm moderately over the whole area, because that would allow them to remain at pretty much optimum levels.

If you have both birds and frogs, you have to find some kind of compromise.

This isn't just an abstract concept. Professor Balmford's team is trying it in Ghana and India, and is starting to be able to make firm recommendations to policymakers.

Land providing food is one example of an "" - a way in which the natural world enables human society to exist.

The , the four-year project that aimed (what's wrong with ambition?) for nothing less that to measure the ecological health of the planet's surface and what it means for humanity, categorises ecosystem services into four groups:

"...provisioning services such as food, water, timber, and fiber; regulating services that affect climate, floods, disease, wastes, and water quality; cultural services that provide recreational, aesthetic, and spiritual benefits; and supporting services such as soil formation, photosynthesis, and nutrient cycling."

In principle, Professor Balmford explained, you could devise the optimum strategy for any given combination of species and services.

This week's conference is necessarily distilling biodiversity science for an audience that contains people in the field but also scientists in completely unrelated disciplines; and in the space of a blog post, I have to distil it down much further, but at some stage all the presentations should be on if you want to explore them further.

Interesting stuff, I hope you'll agree. And we're due to hear more about the economic case for conserving biodiversity - how prices can be put on those ecosystem services, and what it costs to replace them when nature becomes too degraded.

Not everyone thinks likes that approach... but that's a post for another day.

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