Seems like a weird argument. So oil spills in unprotected areas are less serious because nature there is already impacted in other ways? Won't make any difference to the animals and plants in the end.
I do not think this is the point the author tried to make. I read this more like "despite the minor amount of oil spilled compared to other spills, this one will hurt like a big one".
> Although previous oil spills around the world have not been in as environmentally sensitive areas, [my emphasis] they have still significantly affected marine animals and plants.
> In 2010, the Deep Water Horizon incident off the Gulf of Mexico saw nearly 400,000 tonnes of oil spill, resulting in the death of thousands of species ranging from plankton to dolphins.
> There were also other longer-term impacts on marine life including impaired reproduction, reduced growth, lesions and disease.
The article doesn't advocate that oil spills in unprotected areas are less serious, it actually highlights the fact that there are terrible consequences for wildlife regardless of whether the spill site is "protected" or not.