A bit of optimism for your Wednesday: Deforestation of rainforest in the Amazon dropped 27 percent compared to a year ago — the biggest decline since Brazil began monitoring the problem.

From Reuters:

The figures, based on Brazilian government data gathered by satellite imagery, mark the fourth straight year the overall deforestation levels have slowed. …

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Deforestation of Brazil’s Amazon region totaled 4,656 square kilometers (1,798 square miles) between August 2011 and July 2012, a 27 percent drop compared to the same period a year earlier, the Environment Ministry said.

Environment Minister Izabella Teixeira held up the fourth year of slowing deforestation as proof that Brazil is doing its global duty in policing the Amazon basin and curbing illegal loggers and ranchers who clear the forest with fire.

And now, a bit of pessimism.

But the data, scientists warn, must still be fleshed out by follow-up research to confirm whether the reality on the ground matches what seems to be the case from the sky, especially as loggers and farmers clear smaller but more numerous patches of woodland in efforts to evade detection.

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Three of the nine Amazonian states measured in the recent data actually showed increases in deforestation. Meanwhile, scientists and environmentalists warn that changes to Brazil’s environmental policies in recent years could soon begin reversing the progress.

We mentioned those changes earlier this year. The government of Brazil has begun to transition environmental control to local jurisdictions in an effort to reduce costs — which could mean greater susceptibility to abuse.

Over the short term, though, good news. With this announcement, Brazil has nearly reached its goal of reducing deforestation by 80 percent compared to 2005 levels.

Let’s hope it can continue that trend.