Marcelo Elizondo has a regular stop when he takes groups around Playa Avellanas. It is the Icacal estuary, where he points out the different mangrove species and the fish, crabs, iguanas and birds that live among their roots. One day in mid-March 2026 he walked in and found the estuary had stopped moving. A large tide had piled a sandbar across the mouth and closed it completely. The exchange of salt water and fresh water that keeps the system in balance had stopped.
The story of how the estuary got reopened was told in detail by La Voz de Guanacaste in June. The neighbors argued that the rains, which normally fix this kind of blockage, might not come. By October, the national weather service forecast for the North Pacific calls for that kind of dry season.
How a sandbar shuts a mangrove
A closed estuary mouth is a normal part of how coastal ecosystems work. Most years a heavy downpour pushes enough fresh water down the channel to break through the sand and restart the exchange. The Icacal has a complication. Neighbors told La Voz de Guanacaste that the 2012 Nicoya earthquake raised this stretch of coast by a few meters, and that sand has built up more heavily at the mangrove's mouth ever since.
The estuary has been through this before. After the 2012 uplift, sand made it hard for the Icacal to drain to the sea, many mangrove trees died, and machinery was authorized to reopen it. The 2026 episode followed the same pattern, so the community already knew what a slow response could cost.
Elizondo is a biologist as well as a guide. He described to La Voz what he saw once the water stopped flowing: "There was a lot of algae, a lot of dark, stagnant water. When the level dropped the next day we realized a lot of little fish had already died."
From shovels to a formal request
The neighbors tried the least invasive option first and asked for more only after it failed. La Voz reported the sequence this way:
- Mid-March. A high tide builds a sandbar that seals the mouth of the Icacal.
- Semana Santa. About 40 people bring shovels to dig the channel open by hand. The sea fills it back in.
- The letter. Elizondo and the presidents of the Asociación de Desarrollo Específica de Playa Avellanas and the Asociación de Desarrollo Integral de San José de Pinilla write to the Tempisque Conservation Area, the regional office of SINAC. They ask for "a controlled intervention to restore hydrological connectivity." Their reasons are red mangrove dying, the risk of anoxia (oxygen-starved water) and the loss of biodiversity.
- April field visit. SINAC staff see a color change in the white mangrove, probably from salt concentration and stagnant water. They say they need more information and lab analysis, and they do not recommend intervening.
- Second push. The community sends photographs of milky suspended material and an oily film on the water, along with the IMN's projection that El Niño could reach moderate or strong between September and December.
- Authorization. SINAC approves a controlled channel as an adaptive management measure, carried out in coordination with its staff.
The disagreement was about timing
SINAC and the neighbors largely agreed on what was happening in the water. They disagreed about the calendar. In April, SINAC's position was that mangroves return to their usual rise and fall once the rainy season settles in. The community's question, as La Voz put it, was what happens if the rains don't arrive.
Marta Chavarría is a biologist and researcher with the Área de Conservación Guanacaste. She has worked on restoring the Bahía Thomas mangrove in Cuajiniquil de La Cruz. She told La Voz that when authorities have a technical and scientific basis, they should act in dubio pro natura, meaning "when in doubt, in favor of nature." She also said that climate change is making these problems harder and stretching out the natural recovery cycle. That argument is what won SINAC's approval. Waiting for the rains is a reasonable plan when the rains are reliable, and in 2026 they were the uncertain part.
A channel cut so the water could finish it
SINAC attached conditions to the approval. The work had to follow the natural contour of the coastal dune, imitate the way the system behaves on its own, and disturb vegetation and wildlife as little as possible.
Rodrigo Arrea, a coastal engineer who lives in the area, gave technical support. He explained the method to La Voz: "Excavate the whole channel first and then break a plug… that way you take advantage of the water's energy, and it's really the water that ends up making the channel." He called this kind of excavation a "soft measure" and said it is preferable to permanent, damaging fixes such as building jetties or lining river mouths with stone.
The design copied what a strong storm does to a blocked mouth. The backhoe did the work in June because the storm had not come.
The forecast the neighbors warned about
On October 2, 2026, Semanario Universidad reported on the Instituto Meteorológico Nacional's seasonal forecast for October through December 2026. The IMN expects an 80% rainfall deficit in Guanacaste for October and an early end to the rainy season. For the full October–December quarter, the forecast gives the North Pacific the largest shortfall in the country:
- North Pacific: 80% below normal rainfall
- Central and South Pacific: 60% below normal
- Central Valley: 50% below normal
- Caribbean and eastern Northern Zone: normal conditions
Two other details explain the scale. In August, sea surface temperatures in the Niño 3.4 region ran close to 2.5 °C above normal, which the IMN said was higher than during the El Niño events of 1997 and 2015. The same forecast puts Pacific-slope temperatures 1.5 °C to 2 °C above normal for the quarter. The IMN's sub-seasonal outlook for October 26 to November 22 shows a mostly dry pattern, with dry conditions across the North Pacific at the start of November.
For an estuary whose mouth tends to fill with sand, this matters a great deal. A rainfall deficit of that size means fewer of the downpours that normally break a sandbar. When the community made its case in the spring, this was the scenario it described. The June channel gave the Icacal a working mouth before the dry season began. Now that the dry season has come early, the same tides and sand that closed the mouth in March are still at work.
Why showing up helps the mangrove
The sandbar is only one of the threats. In June the Avellanas community listed others: poaching and illegal fishing, contaminated water flowing in from neighboring communities, and trash from both a small illegal dump and visitors to the mangrove. Elizondo told La Voz he hopes to build "a little bridge" someday. He explained that each walk through the mangrove "generates presence," and that someone planning to throw a cast net or hunt a garrobo, a spiny-tailed iguana, might think again if people are around. Along with monitoring and research, the short-term goal La Voz reported is to build people's sense of identity around the mangrove.
One established way in is Elizondo's company, Oropopo Experience. It runs the Avellanas Wildlife Walk, which crosses the habitats the Icacal connects:
- A 2.5-hour, roughly 2-mile loop through forest edge, mangrove, estuary and intertidal beach
- A biologist or naturalist guide, plus a spotting scope or binoculars
- Access to what the company calls the Avellanas Mangrove Bridge and its parking lot, and the story behind the bridge
- A short trail cleanup during the walk, a $2 per person donation to its Mangrove Conservation Program, and 1% of sales to the NGO Funga Conservation
The operator's page lists group walks at 8 a.m. or 3 p.m., with Cabinas Las Olas restaurant as the meeting point. Confirm times and rates with Oropopo before you go.
A walk this season is also a chance to check the estuary's condition yourself. You can see whether water is moving through the mouth, how the white mangrove looks, and whether the milky film from the spring photographs has come back. Those are the same things the community documented to get SINAC's approval in the first place.
The Icacal is part of what sits behind the Avellanas shoreline. If you would like to talk about life on this stretch of Guanacaste, or about property close to places like the Icacal, our Sámara shop at Engel & Völkers Costa Rica is glad to share what our advisors know about this coastline.
