"We can't work, we can't cast a fishing net, we can't take a canoe and go out to fish like before, because we no longer have marshes where we can work," says Anibal Antonio Rodriguez, a 70-year-old fisherman from Nueva Venecia, a stilt-house village in northern Colombia. Once dependent on the marsh for food and livelihood, residents now find their nets tangled not with fish but with Hydrilla verticillata, a fast-spreading Asian plant that threatens to displace them much like violence did in the darkest years of the armed conflict. IMAGES AND SOUNDBITES