How do environmental & ecological issues constitute ethical challenges to business?
Environmental and ecological issues end up being ethical challenges to businesses because the businesses have to figure out how much damage they can ethically do to the environment or ecology in their pursuit of profit.
Many businesses engage in practices that will, to some extent, harm the environment. This is unavoidable since any business that uses any fossil fuels (for example) is harming the environment. But there is surely some limit as to how much harm is acceptable. Businesses must consider this in their attempts to be ethical.
As an example of this, businesses are currently planning to extract oil from the "oil sands" of Canada. This would be profitable but would also help lead to global warming. The firms must decide whether this level of damage is acceptable -- it is an ethical challenge.