Answer:
Requires a difficult set of negotiations: different income levels and set of priorities.
Explanation:
To bring nations of the world to act together in addressing environmental issues that spill over national borders requires difficult set of negotiations between the countries: different income levels and set of priorities.
For example high income countries are the primary producers of greenhouse gases, they might sign agreement with low income countries to reduce their greenhouse effect because most low income countries are still battling of improving food production, healthcare system, and many more so they are not particular about technologies to cause pollution and greenhouse effects. The high income countries can pay low income countries not to produce greenhouse gases which is not their priorities at the moments. Their major priories is the provision of basic necessities of life
