Small-scale fisheries play a vital role in providing food and livelihoods for millions of people around the world, particularly in low-income countries in Africa. However, there is limited statistical data on the composition, abundance, and distribution of the fisheries’ resources, which is crucial for effective management.

New research, recently published in the journal Marine Policy, documents changes in the catches of small-scale fisheries, highlighting a significant decline not only in volume of catches, but also in the size of fish for key local species.

Scientists compiled official catch landing data and combined it with local ecological knowledge from local fishermen and fishmongers on Maio island, in Cabo Verde, designated a UNESCO Biosphere Reserve since 2020.

“Monitoring of fish landings in West African countries is limited and under-represents catches at the local level, especially from artisanal fisheries, creating data gaps that hinder effective management,” says Thais Peixoto Macedo, ICTA-UAB researcher and lead author of the study, who explains that traditional fishers’ accounts revealed trends that are poorly captured in official records. “The findings in this area show us trends that are likely to occur on other islands of the archipelago or other West African coastal areas and should be taken into account in marine resource management plans.”

Local communities believe that certain fishing practices, such as spearfishing with scuba gear and semi-industrial fishing with purse seines and night lights, are major contributors to the decline of fish stocks. In the case of semi-industrial fishing, they report that vessels fish within the three-nautical-mile zone and in marine protected areas reserved for artisanal fishing.

The most reported depleted species include groupers (dusky grouper, island grouper and the African hind) and small pelagic fish such as mackerel and bigeye scad. “According to local fishermen, the decline of small pelagic fish due to semi-industrial coastal fishing is negatively affecting artisanal catches of large pelagic species, such as yellowfin tuna and albacore, an important commercial species for local and international markets,” says Benalsy Varela, FMB staff who contributed to the study. Spiny and slipper lobsters, particularly targeted to supply more tourist-intensive islands, were also considered depleted.

The research highlights a phenomenon known as “Shifting Baseline Syndrome,” where people gradually adjust their perception of what is healthy or natural to a new reality, forgetting past conditions and accepting it as the ‘new normal’. Younger fishermen reported smaller catches and fish sizes than older generations, but a larger proportion of the younger group believe that fish stocks are not in decline.

The study, published Wednesday in the journal Clinical Ophthalmology, is among the first to look into how climate change may affect the eyes.

“The World Health Organization has declared climate change to be “the single biggest health threat facing humanity,” said the study’s lead author Jennifer Patnaik, PhD, MHS, assistant professor of epidemiology and ophthalmology at the University of Colorado School of Medicine. “Yet there are limited studies on the impact of climate change-related air pollution on ocular health.”

The researchers, including Associate Professor Katherine James, PhD, who directs the Climate & Human Health program at the Colorado School of Public Health, examined the associations between ocular surface irritation and allergy-related daily outpatient office visits with daily ambient particular matter (PM) levels in the Denver Metropolitan area.

They obtained data of PM concentrations that were 10 micrometers or less and 2.5 micrometers or less in diameter. The researchers found 144,313 ocular surface irritation and allergy visits to ophthalmic clinics during the study period. The daily visit counts were 2.2 times higher than average when PM₁₀ concentrations were 110. The clinic visit rate ratio increased as daily concentrations increased.

The study reported that conjunctivitis was the second most common eye disease among the clinic visits in the study, representing exactly one-third of all the visits. The prevalence of ocular allergic conjunctivitis has increased worldwide and varies across regions. Socioeconomic and environmental factors such as temperature, humidity and air pollution have been proposed as reasons for the increase.

Patnaik said the health risks of air pollution and climate change span a wide range of outcomes including infectious disease, weather-related morbidity and a variety of lung, kidney and cardiovascular maladies.

“Less studied chronic diseases such as dementia have also been shown to be associated with temperature and air pollutants,” she said. “Research on the topic of ocular conditions and climate is still in its early stages; therefore, more studies are needed to better understand how climate and air pollutants impact eye health.”

James agreed.

“This study highlights the systemic health impacts of climate stressors including air quality, wildfires, temperature, and drought conditions and the continued need to for transdisciplinary research,” she said.

The researchers hope to build and expand on these initial discoveries, said the study’s senior author Malik Kahook, MD, professor of ophthalmology at the CU School of Medicine.

“These findings open the door to a deeper understanding of how environmental factors affect eye health. From a clinical standpoint, we’re now seeing more evidence suggesting that particulate matter in the air isn’t just affecting respiratory or cardiovascular health but also directly impacting ocular surface health,” Kahook said. “Our next steps are to investigate how other air pollutants might influence eye health and to expand our focus to areas outside of Colorado. By doing so, we aim to identify preventive strategies and consider new treatment protocols tailored to address these environmental influences, ultimately protecting the most vulnerable patients in areas heavily affected by pollution.”

Amy Dye-Robinson, from the Department of Biostatistics & Informatics at CU Anschutz, is a study co-author.

From 2015 through 2023, satellite measurements showed that the average amount of freshwater stored on land — that includes liquid surface water like lakes and rivers, plus water in aquifers underground — was 290 cubic miles (1,200 cubic km) lower than the average levels from 2002 through 2014, said Matthew Rodell, one of the study authors and a hydrologist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “That’s two and a half times the volume of Lake Erie lost.”

During times of drought, along with the modern expansion of irrigated agriculture, farms and cities must rely more heavily on groundwater, which can lead to a cycle of declining underground water supplies: freshwater supplies become depleted, rain and snow fail to replenish them, and more groundwater is pumped. The reduction in available water puts a strain on farmers and communities, potentially leading to famine, conflicts, poverty, and an increased risk of disease when people turn to contaminated water sources, according to a UN report on water stress published in 2024.

The team of researchers identified this abrupt, global decrease in freshwater using observations from the Gravity Recovery and Climate Experiment (GRACE) satellites, operated by the German Aerospace Center, German Research Centre for Geosciences, and NASA. GRACE satellites measure fluctuations in Earth’s gravity on monthly scales that reveal changes in the mass of water on and under the ground. The original GRACE satellites flew from March 2002 to October 2017. The successor GRACE-Follow On (GRACE-FO) satellites launched in May 2018.

The decline in global freshwater reported in the study began with a massive drought in northern and central Brazil, and was followed shortly by a series of major droughts in Australasia, South America, North America, Europe, and Africa. Warmer ocean temperatures in the tropical Pacific from late 2014 into 2016, culminating in one of the most significant El Niño events since 1950, led to shifts in atmospheric jet streams that altered weather and rainfall patterns around the world. However, even after El Niño subsided, global freshwater failed to rebound. In fact, Rodell and team report that 13 of the world’s 30 most intense droughts observed by GRACE occurred since January 2015. Rodell and colleagues suspect that global warming might be contributing to the enduring freshwater depletion.

Global warming leads the atmosphere to hold more water vapor, which results in more extreme precipitation, said NASA Goddard meteorologist Michael Bosilovich. While total annual rain and snowfall levels may not change dramatically, long periods between intense precipitation events allow the soil to dry and become more compact. That decreases the amount of water the ground can absorb when it does rain.

“The problem when you have extreme precipitation,” Bosilovich said, “is the water ends up running off,” instead of soaking in and replenishing groundwater stores. Globally, freshwater levels have stayed consistently low since the 2014-2016 El Niño, while more water remains trapped in the atmosphere as water vapor. “Warming temperatures increase both the evaporation of water from the surface to the atmosphere, and the water-holding capacity of the atmosphere, increasing the frequency and intensity of drought conditions,” he noted.

While there are reasons to suspect that the abrupt drop in freshwater is largely due to global warming, it can be difficult to definitively link the two, said Susanna Werth, a hydrologist and remote sensing scientist at Virginia Tech, who was not affiliated with the study. “There are uncertainties in climate predictions,” Werth said. “Measurements and models always come with errors.”

It remains to be seen whether global freshwater will rebound to pre-2015 values, hold steady, or resume its decline. Considering that the nine warmest years in the modern temperature record coincided with the abrupt freshwater decline, Rodell said, “We don’t think this is a coincidence, and it could be a harbinger of what’s to come.”