Trying to keep up with the latest manoeuvrings over Brazil's forest policy is rather like following the country's famous "novelas" or soap operas. Except in this case, the plot is far more complicated and bizarre. So for the benefit of those who missed this week's episodes, here is a quick(ish) synopsis:

Brazil's government delegation at the climate talks in Cancún plays a constructive role in edging towards global agreement on long-term cuts in greenhouse gas emissions, flush with the news that Amazon deforestation has fallen to its lowest level since satellite monitoring began. Meanwhile, back in Brasilia, the leader of the governing Workers' Party in the chamber of deputies, Cândido Vaccarezza, is rumoured to have struck a deal with the Ruralistas (pro-agrobusiness lobby in Congress) that could set off a massive new wave of deforestation and jeopardise Brazil's voluntary but now domestically-binding commitment to cut greenhouse gases. He is allowing a vote (next Tuesday) on a so-called "regime of urgency" for legislation that would weaken Brazil's forest code - the rules that require landowners to keep a certain proportion of  their land in native vegetation and leave forest buffers along rivers etc. NGOs say he is allowing the changes to be fast-tracked in return for support from the Ruralistas for his bid to become house speaker when the new Congress convenes in the New Year - even though the president-elect Dilma Rousseff has pledged to veto any changes that amount to an amnesty for deforesters (which the legislation does, as currently drafted). In an interview with the magazine Época, Vaccarezza is a little less than enlightening:

Época: Did you do this against the will of the government?
Vaccarezza: I did it to avoid the bill itself being voted on this year.
Época: You mean the new [forest] code will only be voted on at the beginning of next year?
Vaccarezza: No, no. Not to be voted the beginning of next year. That's another issue. The deal I made was to vote on the urgency of the bill. Not to vote on the bill this year.
Época: That's what I asked. You will vote on the urgency of the bill and promise not to vote on the Code proposed by deputy Aldo Rebelo [the communist deputy proposing the weakening of the forest protection rules] this year....
Vaccarezze: Vote on the urgency of the bill, but not vote on the bill.
Época: And when will the bill be voted?
Vaccarezza: We have no agreement about when the bill will be voted.
Época: If it's on a regime of urgency, it will be voted at the beginning of next year?
Vaccarezza: No, no. There are bills on a regime of urgency for five years without being voted on.

Roll the credits? Not quite yet. Meanwhile back in Cancún,  Kátia Abreu, president of Brazil's National Agricutural Confederation (CNA) and also senator for the state of Tocantins - location of some of the biggest agricultural expansion into the Cerrado savanna - is speaking at the launch of a new programme of research into sustainable farming for each of Brazil's six biomes. She attacks as "useless" the so-called "legal reserve", the cornerstone of the Forest Code which requires landowners to keep at least 20% of their property (80% in the Amazon) as forest, claiming that there should be a clear separartion of land protected for nature and that used for agricultural production. "If I put a foreign body in a unit of economic production, it will muck up the works," she says. In recognition of her support of Brazil's big-farm interests, Sen. Abreu receives the Greenpeace "Golden Chainsaw" award as she walks through the conference centre in Cancún (see photo) - an honour previously given to Blairo Maggi, former governor of the state of Mato Grosso and big-time soya farmer, now also a senator.

To be continued ....

From tomorrow (Saturday 11th Dec) until Wednesday I will be attending a scientific conference in the town of Bragança Paulista,  organised by FAPESP, the public body that funds scientific research in the state of São Paulo - which contributes about half of all the published scientific papers in Brazil. The theme is "Getting post-2010 Biodiversity Targets Right", and it will bring together experts from around the world to discuss how the strategy for reducing biodiversity loss, agreed at October's UN summit in Japan, can benefit from the latest science and use robust data about the state of life on Earth.

I will be tweeting and blogging from the conference itself, but first here is a preview I did which grabbed the top slot on this week's Science in Action programme, on BBC World Service Radio. It focuses on one of themes of the conference, "Metagenomics as a tool to assess micro-biodiversity". Meta-what? you may well ask, as I did when I read this bit of the programme. But fighting the temptation to allow my eyes to glaze over and move on to some easier concepts, I persevered with some of the abstracts in this section, and realised it was a fascinating field: the use of DNA decoding techniques to analyse the extraordinarily complex communities of micro-organisms that occur in nature - in soils, oceans, plants, etc. Because most of these microbes will not reproduce outside the environment where they have evolved, the standard techniques of culturing bacteria etc in the lab do not work - so the communities are studied as a whole, with samples brought back from the environment and mashed into a kind of soup from which "total DNA" is extracted and identified.

Looking for the fieldwork within easiest reach of my current base in coastal São Paulo state, I was fortunate to come across the work of Professor Márcio Lambais, at the Department of Soil Sciences in the University of São Paulo, based at the ESALQ campus in the city of Piracicaba. His team has been looking at the communities of bacteria that occur in a number of tree species in the Atlantic Forest, one of the most diverse ecosystems on Earth. Lambais has found that the leaves, bark and roots each have distinct, amazingly diverse communities of bacteria that are unique to that species. Not only that - when they took samples from the same species a long distance apart, the bacterial communities changed again. So if a tree species is lost from a particular region, literally thousands of bacteria species go with it. So what? Well, I discuss some of the implications in the BBC report, and for those wanting a more in-depth discussion of the research I am posting here a full version of the interview I did with Márcio Lambais in a small forest adjoining his campus in Piracicaba.

Today's announcement of the lowest level of Brazilian Amazon deforestation since the start of satellite monitoring in 1988 deserves to be celebrated, and it has been by out-going President Lula and his ministers - with perfect timing for them as they start negotiations at the Cancun climate talks where reduced deforestation is a major issue.

So the rest of this blog is going to seem very churlish as I add some context which takes a little bit of the shine off that main headline.

The first point to make is that the figure - 6,450 square kilometres of forest clear-cut in the year up to August 1st 2010 - is considerably higher than many of the predictions, which had forecast a fall to around 5,000 square kilometres based on the preliminary month-by-month monitoring. It is a cut of around 14% on the figure for the previous year (7,500 sq km) and still means an area larger than the state of Connecticut was cleared in 2009-10.

Even so, when you consider that an area of the Amazon more than four times that size went under the chainsaw and the torch in 2003-4, the scale of the progress must be acknowledged.

One reason for caution was highlighted by the director of the Brazilian National Space Research Agency (INPE), Gilberto Camara, as he delivered the presentation at the press conference to launch the monitoring results in Brasilia, with President Lula himself in attendance.

He helpfully emphasized the point on Twitter (@gcamara), advising his followers to check out the slide reproduced below.

To translate the text for non-Portuguese speakers, the heading reads "Deforestation by size" and the bottom notes, "Cutting less than 50 hectares: 35% of the total in 2002, 80% of the total in 2010.

In other words, there has been a very significant change in the pattern of deforestation since that high point in 2003-4: the very large mass-clearances, for example by soya farmers and big-time cattle ranchers, have to a large extent been brought under control, so what remains is a  large number of smaller acts of deforestation.

You could say that is good news, reflecting the pressure imposed on the big-time deforesters by Brazilian government action, international consumer pressure and indeed the policies of Brazilian stores including Walmart refusing to source beef from ranches associated with deforestation.

Even so, as Camara notes, it makes the continued decline of deforestation that much more challenging to achieve: how to monitor and control the remaining destruction when it is so dispersed?

"“After a fall of 45 per cent in deforestation in 2009, we had another 14 per cent in 2010. Each year, reducing deforestation will become more difficult,” Camara said on Twitter.

Another, linked trend is confirmed in these figures - a shift of focus away from the so-called "arc of deforestation", that swathe of land to the South and East of the Amazon biome which has seen the main advance of the agricultural frontier in recent decades.

As the two charts above show, the states in which that frontier is concentrated, Mato Grosso, Pará and Rondônia, have all seen declining trends in deforestation which have continued this year. States such as Amazonas and Acre, on the other hand, where a vast majority of the forest area is so far still intact, saw increases in deforestation this year, albeit still at a relatively low level. It is a warning sign that new frontiers may be opening up, and these trends could be very challenging to control.

I could go on to catalogue some of the remaining concerns: the possible impact of loosening Brazil's Forest Code, which could be voted imminently in the Congress (see last but one post); the impact of current projects to improve highways and build dams; the renewed pressure from a reviving world economy and additional demand for the agricultural commodities driving deforestation; and the likelihood of displacing deforestation to other regions, in particular the ultra-diverse Cerrado savanna which is disappearing at more than twice the current rate of the Amazon.

But who am I to be the Cassandra on the day Greenpeace Brasil issued a release headlined "Another nail in the coffin of deforestation"? It referred not to the INPE figures, but to an announcement by Banco do Brasil that it would deny credit to soya formers who planted in recently-deforested areas.

So for now, Brazil is well on track to meet its pledge to reduce Amazon deforestation by 80% before 2020. The world will be watching and hoping this trend continues.