agriculture amazon rainforest assarting australia biochar biodiversity biodiversity action plan brazil charcoal chestnut coca colombia crop rotation deforestation desertification ecology endangered species europe finland firewood forest girdling habitat hoe-farming holocene extinction event hunter-gatherer india indochina indonesia livestock madagascar mexico milpa neolithic revolution north america norway nutrient opium poppy overpopulation ph pasture phosphorus population population growth rainforest rough pasture russia sahara sahel scorched earth secondary forest shifting cultivation slash-and-char south america species surface runoff svedjebruk sweden teak terra preta transhumance tropics vegetation wildfire woodland woodlands zambia zebu