Several news stories caught our attention this week on how Earth Observation (EO) satellite data is being used to monitor the impacts of climate change: global warming, coral bleaching, and flamingos!
Global Warming
Last week the European Union’s Copernicus Climate Change Service (C3S) confirmed that the global surface air temperature for March was 14.14°C, 0.73°C above the thirty year average for the month of March, and 0.10°C above the previous March high from 2016.
In addition, C3S also confirmed that:
- March 2024 was the tenth consecutive month recording the hottest ever temperature for that month in the ERA5 data record going back to 1940,
- Global oceans have seen 12 consecutive months of record high sea surface temperatures, and
- Global average temperature for the last year, April to March, is hottest on record 0.70°C above the thirty year average.
The ERA5 data record is managed by the European Centre for Medium-Range Weather Forecasts (ECMWF) and provides hourly estimates of a large number of atmospheric, land and oceanic climate variables. It is currently produced by the C3S and uses a numerical weather prediction model to combine a variety of observations, including satellite and ground-based measurements to produce its records; the dataset extends from January 1940 to the present day.
Coral Reefs
Following on from the information about record sea surface temperatures, this week the United States’ National Oceanic & Atmospheric Administration (NOAA) reported that the world is, once again, undergoing a global coral bleaching event.
The first global coral bleaching event occurred in 1998, the second in 2010, and the third between 2014 and 2017 – we wrote about the third event in a previous blog. A global bleaching event is declared when at least 12% of corals in the three main oceans experience heat stress high enough to cause bleaching.
Coral bleaching occurs when water stresses cause coral to expel the photosynthetic algae, which give coral their colour, exposing the skeleton and turning them white. The stress this time is mostly due to higher seawater temperatures with extensive bleaching seen across the Atlantic, Pacific and Indian Oceans over the last 14 months, with around 54% of waters with coral reefs impacted.
NOAA use data from their own EO, and other partner, satellites to monitor sea surface temperature, and have a dataset going back almost forty years. The image at the top of the blog shows the high levels of marine stress with high levels in both hemispheres from January last year until the present day. During this period, mass bleaching of coral reefs have been confirmed across the globe. While bleaching does not kill coral immediately, it does put them at a greater risk of mortality from storms, poor water quality, disease and the crown-of-thorns starfish. Equally, if the marine heat stress reduces, corals can recover.
Flamingos
Finally, there was an interesting paper published by Byrne & Tebbs et al in the journal Current Biology on the April 12th, 2024, titled ‘Productivity declines threaten East African soda lakes and the iconic Lesser Flamingo’.
In the paper, the researchers detail their work comparing satellite EO and Lesser Flamingo observations to monitor what is happening to the species and its habitat ecosystems at 22 soda lakes across East Africa. A soda lake is a highly productive aquatic ecosystem as it’s a strongly alkaline and saline water body, with a pH value between 9 and 12, allowing it to sustain the unique phytoplankton communities eaten by the Lesser Flamingos.
This is the first time EO data have been used to monitor Lesser Flamingos. The researchers used surface reflectance and top-of-atmosphere reflectance from Landsat 5 Thematic Mapper and Landsat 7 Enhanced Thematic Mapper. A Modified Normalized Difference Water Index (MNDWI) was applied to estimate lake surface areas, and they also used a number of algorithms to calculate lake surface temperatures, chlorophyll-a concentrations and cyanobacterial blooms. Lesser Flamingo count data for Kenya and Tanzania, for the period 1990 to 2017, was obtained from the International Waterbird Census (IWC) global wetland monitoring programme.
The researchers determined that more than three-quarters of Lesser Flamingos inhabit the soda lakes of East Africa, and their populations are in decline. They felt this decline was most likely caused by a reduction in the phytoplankton biomass in the soda lakes, which had shown a significant reduction over the 23 years of the study (1999 to 2022) linked to rises in lake water levels, diluting the alkaline and saline content, from increased rainfall. Unless improved soda lake monitoring and ecosystem preservation practices are enacted, then soda lake ecosystems, and in turn Lesser Flamingo populations, will be impacted – including potentially moving from their traditional feeding and breeding areas.
Conclusion
Changes are happening in the climate across the planet, and EO offers a method of monitoring the change and the impact it has having on ecosystems around the world.
