The Curlew describes itself as a: ‘high-quality periodical dedicated to fine writing about the natural world’. The journal is published on a quarterly basis: the next deadline is the end of February 2017. There is no payment, but the editors state that proceeds will go to support conservation projects. Submissions information here. There is even a section for work by under-16-year-olds: http://www.the-curlew.com/sanderlings
The Verve Poetry Festival in Birmingham, UK, has a competition this year, for poems that mention the city of Birmingham! There is a charge for adults to enter (judge: Hannah Silva), but: “The children’s category is open to any child in Year 11 or below in September 2016 (UK) or aged 15 or under on 1st September 2016 (non-UK).” The judge for the Children’s Category is Emma Wright, who runs The Emma Press. Deadline for both children and adults (new, extended deadline for the latter- ignore any references to an earlier date) is 30 September. More information here.