Responsibility? I guess it depends on how responsible you feel.

What can you do? One of the easiest things is to stop eating meat.

http://www.onegreenplanet.org/animalsandnature/beef-producti...

Brazil is failing for roughly the same reasons as most of the rest of South America: excesses of state power, which are too attractive for business to pass up.

The economy is depressed by excessive policy, the people have bigger problems than the destruction of the Amazon. In addition, because the government owns the woodland, there's basically no reason to replant or maintain, which means that if you want lumber you have to go into old growth forest.

That's not the reason. Here in Bavaria most of the forests are in the hand of the state and there are growing forests since roughly 100 years.

More likely a driving force is the internalization of agriculture. All the cows and pigs raised in Europe are fed with south-American soy.

I wish someone knowledgeable about forestry could explain why replanting is not done. What are the costs and subtleties, beside political friction I mean. Or maybe it's only political.

Replanting is only done when economically viable and future "land use" is for regeneration of the harvested species. This is done is Pacific Northwest of the US for Douglas Fir. Replanting isn't used in US Northern Hardwood production as the stands are cut to retain trees that reproduce and in another 15-30 year period another variable retention harvest is performed [1]. Modern forestry leverages ecological theory such as disturbance regimes to mimic changes and diversify the timber stands for risk management and ecological factors [2].

[1] https://en.wikipedia.org/wiki/Variable_retention

[2] https://andrewsforest.oregonstate.edu/sites/default/files/lt...

A lot of the cleared land is used for cattle grazing.

You've been downvoted but your answer is spot-on.