I had posted this previously and the experts felt the question was not mentioned although it was. Please answer this question.
The poem does not make a clear mention of what the letters are about, though it does mention that they are not about the loss of green cover due to felling of trees. This is a clever technique by the poetess to draw attention to deforestation. This poem has underlying tones of feminism. She does not mention about the departure of the trees in explicit terms as she is in favour of them moving out towards an open space. She wants them to be a part of Nature where they originally belong. This is a metaphor for her support of freedom for all human beings. This further implies her belief in feminism.