The Colombia Guide

Cartagena's Coral Reefs Get New Protection Zone as Bleaching Threat Grows

· 3 min read Travel News
Clear turquoise water and coral reef near the Rosario Islands, Colombia

Contents

  1. The Scale of the Problem
  2. What the New Rules Mean for Visitors
  3. Signs of Recovery Already
  4. What to Expect as a Traveller

Colombia’s Ministry of Environment declared a new marine protected zone (MPZ) covering approximately 2,400 hectares of reef system around the Rosario Islands in April 2026 - the largest reef conservation measure in the Cartagena region in more than a decade. The designation comes in direct response to bleaching episodes that damaged an estimated 18% of the shallow-water coral cover around the islands in 2023–24, driven by elevated sea surface temperatures in the southern Caribbean.

The Scale of the Problem

The Rosario Islands sit about 35 km southwest of Cartagena and have long been the primary snorkelling and diving destination for visitors to Colombia’s Caribbean coast. The coral communities here are part of the Seaflower Biosphere Reserve, and the islands see an estimated 300,000 tourist visits per year. That volume of boat traffic, combined with warming waters, has placed pressure on reefs that were already stressed by earlier bleaching events in the 2010s.

Coral bleaching occurs when water temperatures rise by as little as 1°C above seasonal norms for extended periods, causing corals to expel the algae that give them colour and nutrition. Without recovery time, bleached corals die within weeks. The 2023–24 event was the most severe recorded in the Rosario Islands area, prompting researchers from Universidad de Cartagena and the Invemar marine science institute to push urgently for expanded protections.

What the New Rules Mean for Visitors

The MPZ introduces a zoning system. A core no-entry zone covers the most damaged reef areas and is closed to all boat traffic, snorkelling, and diving for a minimum of three years while recovery monitoring takes place. A buffer zone surrounding the core allows non-motorised activities - snorkelling and freediving - at designated sites approved by the Parques Nacionales Naturales authority.

Visitors taking day trips from Cartagena should expect to find that some of the snorkelling spots that were popular five years ago are now off-limits or replaced by alternative sites. Licensed tour operators have been briefed on the new boundaries and are required to use GPS-marked routes. Anchoring on reef is now prohibited throughout the entire island group, and a mooring buoy system is being installed at the 12 most-used sites.

Signs of Recovery Already

Despite the damage, marine biologists monitoring the Rosario reefs reported in early 2026 that coral recruitment - new coral polyps settling on reef substrate - had increased significantly at several protected sites. This is considered an early positive indicator. The no-take fishing zone around the islands, which has been in place since 2020, appears to have contributed to healthier fish populations that help keep algae from smothering recovering corals.

What to Expect as a Traveller

The reef at the Rosario Islands remains worth visiting. Healthy sections with fish diversity and intact coral formations still exist, particularly at depth - recreational divers reported excellent visibility and healthy wall dive sites at 15–25 metres in 2025. Day-trip operators from Cartagena continue to run snorkelling excursions, and the new mooring buoys mean boats are causing less damage than before.

If you plan to snorkel or dive, choose an operator who is registered with ProColombia and can demonstrate compliance with the new MPZ rules. Expect to pay approximately COP 120,000–180,000 for a day-trip including snorkelling, lunch, and round-trip transport from Cartagena as of mid-2026.