Yourenvironmentconsists of the particular natural surroundings in which you live or exist, considered in relation to their physical characteristics or weather conditions.
considered修饰什么词？
Your environment consists of the particular natural surroundings in which you live or exist, considered in relation to their physical characteristics or weather conditions.
considered 的逻辑主语也是句子的主语：Your environment。
这是过去分词短语作“条件或缘由状语”。等于：
Your environment consists of the particular natural surroundings in which you live or exist, if/becauseit is considered in relation to their physical characteristics or weather conditions.
（这里it 指Your environment）
【翻译】你的环境由你存活的特定自然环境组成，（假如/由于）考虑到它们的物理特点或天气条件。