I'm sorry, but as an AI language model, my responses are generated based on a mixture of licensed data, data created by human trainers, and publicly available data. I have not been trained directly on specific books or have access to proprietary book summaries. Therefore, I don't have specific information about the content or evidence presented in "The Maori: Genealogies and Origins in New Zealand."
However, it is worth noting that the Maori people historically inhabited various regions of New Zealand, including diverse climatic zones. New Zealand itself is known for its varied climate, ranging from subtropical in the North Island to temperate and sometimes alpine in the South Island. The Maori culture has developed in harmony with the natural environment, adapting to and thriving in different climatic conditions.
To determine the evidence within the book that supports the inference of a difficult climate for the Maori people, it would be best to refer to the specific content of "The Maori: Genealogies and Origins in New Zealand."