In the survey Vecinos conducted in July, thirty percent of respondents (including me) said they weren’t sure if the sargassum barrier on Half Moon Bay was stopping turtles from nesting or not. We all want to protect the turtles, so I thought would be useful to look at the most recent nesting data. Attached are two charts showing nest counts collected by CEA for the past three seasons on HMB and on Akumal Bay, including 2023 through August 15th. 

The HMB chart shows that the 2023 season started later on HMB than the 2021 and 2022 seasons, causing great alarm in the community. But over the past six weeks, nest counts have accelerated on HMB and are now ahead of the 2021 pace and are approaching the 2022 pace, which is encouraging. 

The slow start to the season on HMB this year could be due installation of the barrier, to sargassum on the beach blocking turtle access, to other factors, or to a combination of factors. The recent acceleration in nesting on HMB could be due to beach cleaning done by ZOFEMAT and others, by the turtles adjusting to the new barrier over time, or other factors. 

However, the Akumal Bay chart shows that the 2023 season started on time on Akumal Bay and is running significantly ahead of both 2021 and 2022 through August 15. So, why is nesting way up in 2023 on Akumal Bay but not on HMB? And why did the 2023 Akumal Bay season start on time while the HMB season started late? Those seem like warning signs.

I’m not making a case one way or another about the impact of the HMB sargassum barrier on turtle nesting - I'm just reporting data. It's very difficult to get clear cause and effect answers about a live ecosystem that even experts don't fully understand, but I think we should be discussing it using facts and data, and these are the best nesting data we have, as far as I know. 

I find these charts to be inconclusive about the effect of the barrier on turtle nesting. I see both warning signs and signs of improvement, but I don't see clear evidence of either zero impact or a disastrous impact.

What do you think? Do you interpret the data differently than I do? Are there other data you can add? Let’s talk about it.

Half Moon Bay is off to a fast start in 2024 (yellow line), similar to 2021 (blue line) and faster than both 2022 (orange line) and 2023 (gray line). But 2021 (with no barrier) ended up with fewer than half the number of nests of either 2022 (with no barrier) or 2023 (with barrier). Nesting in 2023 lagged 2022 by about two weeks for comparable counts until the end of August, but caught up in September and ended higher than 2022.

One more turtle nesting update.

Nesting season is almost over. The 2024 season started fast on HMB, but it's turning out to have the fewest number of nests of the past three years.

Earlier in this thread, there was a claim that the fast start in 2024 compared to the slow start in 2023 "proved" that the sargassum barrier had stopped turtles from nesting in 2023. But a fast or a slow start doesn't predict how the season will end up. It's impossible to attribute the results to any one factor, including the barrier and anything else.

Nature is complicated.