This paper reflects on how the mainly intention-based ethics of Buddhism relates to issues of causing unintended harm across a range of issues of relevance to environmental concern, such as species protection, resource depletion and climate change. Given our present knowledge, is environmental concern to be seen as morally obligatory for a Buddhist or only a voluntary positive action? Writers sometimes simply assume that Buddhist ethics are supportive of the full range of environmental concerns, but this needs to be critically argued. The paper reflects on a range of principles of traditional Buddhist ethics, both Theravāda and Mahāyāna, and concludes that, in the present world context, Buddhist considerations urge not only that we should not deliberately harm any living being, but that we should also look after the biosphere-home that we share with other beings, by using our knowledge of unintended effects of our actions to modify our behavior, and that we should act positively to benefit others beings, human and non-human, and enhance their supportive environment. The paper also considers issues such as Buddhism's attitude to wild nature, industrialization and "progress."