Presidential candidate Donald Trump regularly talks about building a wall - a huge wall - between the U.S. and Mexico to keep out immigrants. It's a popular, but short-sighted idea that not only won't work, but misses the elephant in the room that will intensify pressure northward: climate change.

Here's what we know: Droughts south of the border will get worse, requiring shifts in agriculture and land use. Sophisticated scientific models predict a dramatic decline in crop yields, putting more pressure on limited resources.

What this means is that more people will seek entry over the border into the United States. A lot more.

A recent article from Proceedings of the National Academy of Sciences predicted that the U.S. would receive millions of new immigrants from Mexico due to the effects of climate change over the coming decades.

So how can we prepare? Well, a wall certainly won’t solve the problem. Not to mention it's very, very, very challenging - if not fantasy - to pull off. We need solutions grounded in reality, and a primary focus should be on improving our energy policies at home.

Mitigating greenhouse-gas emissions will be an important early step, and the good news is that we're already on a path to do it. As the U.S. energy sector becomes cleaner and more efficient, we will reduce the climate-induced pressure anticipated to drive millions of people over the border.

As for dealing with immigration more broadly, there's no single easy answer. Sure the popular talking point about a wall may garner applause, but it's too simplistic and carries very little substance. The United States will need comprehensive interdisciplinary policies in order to deal with building pressure at the border due to climate change.

Given that immigration is going to feature prominently in the race to the White House, let's make sure it's grounded in reality.