The phrase "massive swaths" refers to large areas or portions. It means a significant or substantial amount of something, such as land, population, or a range of something that covers a wide extent. Full definition
Those revisions saw the removal or rewriting of massive swathes of copy - and - paste scholarship, as well as correction of many errors identified by myself and others. (realclimate.org)
The report from the Canadian Boreal Initiative and the Boreal Songbird Initiative, entitled «The Carbon the World Forgot», estimates that the boreal forest — which survives in massive swathes across Alaska, Canada, Northern Europe, and Russia — stores 22 percent of all carbon on the earth's land surface. (news.mongabay.com)
From Midwest «missionaries» to Wall Street speculators, investors are grabbing massive swathes of common land, says Fred Pearce, especially in Africa (newscientist.com)