There are, broadly speaking, two types of arguments connecting universal basic income (BI) to ecological purposes. The first, “minimalist”, ecological argument is an argument for carbon dividends. Carbon dividends are per capita cash payments distributed periodically to everyone from the revenue from carbon pricing, either carbon taxation or a carbon cap with an auction of emission permits. Carbon pricing is essential for meeting internationally agreed upon climate mitigation goals. Using most of the proceeds for dividends is crucial for rectifying the otherwise unjust effects of a regressive tax, and for making a steadily rising carbon price politically feasible. Thus, the minimalist ecological argument for BI is a strong argument. However, carbon pricing can yield at most a partial BI, insufficient for basic needs. The second argument, the strong or “maximalist” ecological argument, concludes that a full BI funded from sources in addition to carbon pricing can or will have positive ecological effects. The minimalist argument has been widely discussed, has many supporters, and is a strong argument. The maximalist argument has received less attention. This chapter focuses on the maximalist argument, evaluating its premises, including that a BI will facilitate a post-growth economy by freeing people to spend more time in less carbon-intensive activity, by facilitating work-time reduction and work sharing, and by reducing inequality. The initial hypothesis is that the maximalist argument is weaker than the minimalist argument. This is partly because some of the maximalist premises support egalitarian redistribution but not specifically in the form of basic income, and partly because some claims about alleged effects need further empirical support. The argument could be strengthened by making the case for BI over other forms of egalitarian redistribution and by empirical research on the ecological effects of BI.