Beaches are far more than just places to hang out and enjoy the ocean. They are also buffers that take the brunt of crashing waves and save the land behind the beach, where people live and work, from being washed away. A new study has taken a stab at figuring out just how much land we could lose this century due to sea level rise, how many people will be forced to move and how much it will all cost. It also looks at what could happen if we try and fight back by artificially adding sand to beaches.

“Across the...scenarios (we) considered, large areas of land could be lost if there is no adaptation," explained Jochen Hinkel of the Global Climate Forum in Berlin, Germany and first author on the new paper published in the journal Global and Planetary Change. "This paper presents a first assessment of the global effects of climate-induced sea-level rise on the erosion of sandy beaches” and the loss of land that, in turn, forces people to move.

PHOTOS: 9 Popular Cities Losing War with Rising Seas

The five countries that will be most affected by land loss by 2100 are the United States, Australia, Mexico, Russian Federation and Brazil. These countries all have a long coastlines and lots of sandy beaches. As might be expected, four of these countries are among the top five countries in terms of their total length of sandy beaches: Australia (8,200 miles or 13,200 km), United States (8,000 miles, or 12,800 km), Brazil (3,800 miles, 6,100 km), Denmark (2,900 miles, 4,600 km) and Mexico (3,000 miles 4,900 km).

The team used six global mean sea-level rise scenarios for the 21st century, ranging from 0.2 to 0.8 meters, and six socio-economic scenarios. They also looked at what could happen with and without beach nourishment programs, like those that keep tourists coming to beaches in Florida.

Without beach nourishment, global loss of land could be 6,000 to 17,000 square kilometers (2,300 to 6,600 square miles) during the 21st century. If you packed all that land loss together, the area is comparable to the entire state of Delaware up to the entire state Hawaii. Spread out globally, however, that erosion would lead to the forced migration of between 1.6 and 5.3 million people at a cost of between $300 billion and $1 trillion, the researchers report.

The good news is that bringing in more sand, a process called beach nourishment, could really help. Some eight to 14 percent less land might be lost and 56 to 68 percent fewer people would have to move in this century. That could reduce the cost of forced migration by about 80 percent; bringing the financial burden of moving people to somewhere between $60 to $200 billion.

Top 10 Beaches of 2013

In terms of absolute costs, the five countries most affected would be the United States, Japan, Germany, Denmark, and the Netherlands. But if you read that in terms of a country's overall human displacement costs, Kiribati, The Marshall Islands and Tuvalu pop to the top of the list.

Beyond the scope of the study, but related to it are the effects of beach losses on wildlife -- something of concern to sea turtle advocates, for instance.

"It's interesting that the Climate Action Plan by (Southeast) Florida counties (the best Sea Level Rise adoption effort to date in Florida) does not even mention beaches," noted Gary Appelson, policy coordinator for the Sea Turtle Conservancy. That said, sea turtles really don't need the wide beaches that humans prefer.

"Sea turtles do fine on high energy, very narrow beaches," Appelson said. "The problem is when we line these beaches with structures and infrastructure and the beach looses resiliency to recover from storm events." Just how that plays out in beach nourishment scenarios remains to be seen.