Using Hippos to control Water Hyacinth in the Delta. A stroke of genius. Maybe. One of the problems with the oversimplification of problems, a al Donald Trump, is factors that are ignored, brushed aside, misunderstood, or unanticipated. The use of exotic species to control other invasive species doesn't normally go well. Cases in point are the Mongoose in Hawaii, Cane Toads on Pacific islands to control Monitor Lizards, Gambusia (mosquito fish) to control mosquitoes.
Yet, here is an ingenious plan to use gigantic mowing machine herbivores to control Water Hyacinth. One hopes it will work.
If anything, these are technological fixes for technological disasters.
Here's where I invoke my theory of the burden of engineering: the impossibility of design of perfect systems by the Human Brain. It's not that the human brain is deficient, but we evolved to SOLVE problems, not to anticipate them. Take the history of science and technology: scientific knowledge has grown incrementally, each step depending on the previous one. So, for example, as the tale goes, Newton and Leibnitz concieved of Calculus co-temporally. Without the Shoulders of Giants upon which to stand, would this next step have been possible?
Bikini Atoll: a concrete dome is constructed to contain the genie, after it was released from the bottle. Years later, who anticipated that Sea Level Rise would render this solution moot? Like the possibility of space travel without an incident, or the engineering of a perfect, unsinkable ship, biological systems would seem equally to impossible to engineer perfectly. We can anticipate many potential consequences, but can we foresee every one?
Pacific Islands are microcosms of, say continents, or of larger islands. Just as it is impossible to turn back the clock, I would argue that, should any single example of intervention in previous invasions appear to be successful, then who can say there are no overlooked or unknown consequences?
One hopes that Hippos will be able to clear the waterways of weeds. What could go wrong?