Mongabay: Marina Silva, the charismatic rubber tapper who went on to become senator and Environment Minister, is weighing a presidential bid in Brazil’s 2010 election, according to multiple reports. Political observers say that while her chances are long, Silva’s entrance and focus on the environment could spur interest among Brazilians disenchanted by the Workers’ Party, the dominant part which has been tarnished lately by corruption scandals. “Marina excites young people, those who are …