There has also been concern that a land-based link would hamper the containment of foot-and-mouth disease that was eradicated from North America, and there are

There has also been concern that a land-based link would hamper the containment of foot-and-mouth disease that was eradicated from North America, and there are environmental concerns. Colombia proposed building a road through the whole gap: https://www.latimes.com/archives/la-xpm-1995-08-20-mn-36988-story.html https://www.latimes.com/archives/la-xpm-1995-08-20-mn-36988-... But this has been heavily protested by environmentalists and natives alike. It might be less controversial to go northeast to Acandí by tunneling under the mountains, which would leave almost all of the forest untouched. Then you could build a long bridge, a coastal highway, or just keep using the ferry.