Addressing the geographic bias in environmental monitoring: example of a coral bleaching database

Monitoring coral reefs in Butaritari, Kiribati (2012)

When I first studied ecology, I was struck that so many of the influential research findings came from the same few locations. Often this is because the geographic characteristics or the history of the particular country, island, coastline, or lake makes it ideal for testing a scientific hypothesis (e.g., Barro Colorado Island, which was created by the Panama Canal) or representative of something that is common in other locations (e.g., Experimental Lakes Area in Ontario, a good proxy for northern lakes).

It also a question of logistics. The resources for environmental monitoring – the equipment, the expertise, the money – are not evenly distributed around the world. While scientists do choose field sites based on ‘science,’ we also have to weigh the optimal locations for answering key scientific and societal questions against the infrastructure available and the basic ability to complete research in those locations. No funding agency will support a project unless you can show that it is feasible.

So environmental research and monitoring tend to cluster in places with available resources. Hubs develop. For coral reef research, the hubs include parts of the Great Barrier Reef, the western Indian Ocean, the Galapagos, Hawaii, and the Florida Keys. In choosing to do field projects in the central equatorial Pacific, I am probably tipping that science vs. logistics scale so much towards ‘science’ that it is liable to break, which may explain my growing familiarity with tropical infectious diseases.

This geographic bias in environmental monitoring is essentially the reason behind our work on a new global database of coral bleaching events published in PLoS-One and described in this CBC video:

For as much as bleaching is of interest to scientists, to funders, to divers, and to the public at large, countless bleaching events go unreported or unstudied. The majority of tropical reefs are in developing countries where the capacity for extensive monitoring is limited, either because of the available resources or the remote nature of the reefs.

We tried to fill the gaps by searching the literature and the coral reef science community for reports missing from Reefbase, the existing voluntary database used by scientists, and by spatially interpolating the information that was available. The process produced a database with two components: one is a set of the actual observations, and one is a set of gridded (4 km x 4 km resolution) interpolated maps of the probability that bleaching occurred each year across the world.

The observed database, as described in the paper, has 79% more records than were in Reefbase. The number of reports gives a sense of how coral bleaching has become a more common occurrence in the past few decades. Of the 7429 reports, only 250 occurred before 1990!

The more comprehensive observed database cannot fill the gaps where no monitoring occurred. There remains a large, unknown area of unobserved past bleaching (possible “Type II errors” or “false negatives”). The spatial interpolation was an attempt to fill that gap. At left is an example of the before (top, observations only) and after (bottom, interpolation) from the Caribbean in 2005.

Using the interpolated maps, we found that the area of coral reefs with >50% probability of bleaching was eight times higher in the second half (1999-2010) of the time period studied (1985-2010). We also contrasted the bleaching probabilities with past temperature data and found that the higher the probability of bleaching, the higher the heat stress (measured as “degree-heating-weeks”) that the coral reef experienced. Put this all together, and it is yet more evidence that coral reefs have experienced more frequent and more severe bleaching over the past few decades because of rising ocean temperatures.

This work is only beginning. Version 1 of the database can be downloaded here. We’re also hard at work on version 2, which will include data through the end of 2016. So please share any and all reports of coral bleaching, particularly any older reports that are not described in the existing literature.

The Great Barrier Reef and the voice of scientists in the Trump era

The incredible warmth of the past two years laid waste to corals on the Great Barrier Reef. A new study, led by Terry Hughes and a large team of top Australian scientists, finds a strong correlation between the warm ocean temperatures over 2015/16 and the extent of coral bleaching, an often fatal paling of the colourful reef-building animals. The study also finds that there are very few stretches of the Great Barrier Reef left (<10%) that were not affected by the 3 large-scale bleaching events over the past 20 years.

The authors soberly conclude:

Securing a future for coral reefs, including intensively managed ones such as the Great Barrier Reef, ultimately requires urgent and rapid action to reduce global warming.

I wish I could say that this widespread death of corals comes as a surprise. It doesn’t. Scientific research, including my own, has been warning for almost two decades that the fate of the world’s coral reefs depends on actions to slow global warming. A look back at some old work on the subject shows just how critical a time this is for the climate, for coral reefs, and for scientists.

In a 2005 study, my first on the subject, a group of colleagues and I used the results of climate model simulations and data derived from satellites to assess how the likelihood of coral bleaching-level heat stress will change as the planet warms. This figure from the paper is an example of the projected frequency of bleaching ‘alerts’ during the 2030s in a business-as-usual emissions scenario using a particular model (brighter colours = higher frequency):

The green dots around the central Great Barrier Reef represent a bleaching-level heat stress occurring every 3-5 years. The orange dots around the northern Great Barrier Reef represent bleaching-level heat stress at least every 2 years, far too rapidly for many coral reefs to recover. Fast-forward another 20 years to the 2050s, and all of the Great Barrier Reef, as well as 98% of the rest of the world’s reefs, appear in red: bleaching-level heat stress happening every year.

The study ended as follows:

To ensure the world’s coral reefs are protected from climate change, the margin for error on emission controls may be small.

That statement rings true today, in more ways than one.

The research study arose out of a collaboration that I had arranged with scientists at NOAA. At the time, the George W. Bush Administration was clamping down on climate change research and communication of that research by federal agencies. The restrictions led to all manner of absurdities. Before giving a talk about the planned collaboration to a NOAA climate panel, I was actually cautioned not to say the words “climate change,” even though my talk was titled “Climate change and coral bleaching.”

When we finished the final draft of the paper, we realized that the higher-ups, who had to approve of work co-authored by NOAA researchers, were likely to object to the policy-tinged language in the conclusion. What to do? Changing a conclusion that flowed logically from the results was out of the question; even if we were open to a change, it seemed crazy to bend a scientific paper to suit the U.S. government when the lead author was not a government employee, let alone even an American.

Instead, we massaged the author list and the author information to avoid crediting NOAA and a political review of the work. One NOAA person involved in the project, albeit very peripherally, offered to not be listed as an author. It has always bothered me.

Today, the story of publishing that paper sounds almost quaint. The ‘war’ on science of the Bush years now looks like a minor skirmish compared to the nuclear holocaust of funding cuts, denialism, and obstructionism being pushed by the Trump Administration. And it is happening at the same time when scientists are pondering funeral arrangements for one of the natural wonders of the world, and pointing the finger at climate change.

There’s no sense wondering anymore if it is appropriate for scientists to speak up and be heard. We should be shouting from the rooftops.

Seriously, if not now, when?

Can coral reefs recover from bleaching? The case of Tobago

by Salome Buglass

The bleaching of coral reefs is once again making headlines. Reefs across the tropical Pacific, including the Great Barrier Reef and now reefs in the Indian Ocean, are turning white due to warmer than usual sea temperatures as a result of climate change and the current El Niño. This may be the beginning of a series of mass bleaching events occurring at a global scale, similar to those observed in 1998, 2005, and 2010. Caribbean coral reefs may be the next to experience extensive bleaching, starting at the end of the region’s summer (~August 2016). How coral communities recover from the aftermath of bleaching events is a key question concerning marine scientists and managers as it will determine the survival of coral reefs on an increasingly warming planet.

Bleaching in 2010 at Speyside, Tobago

Bleaching in 2010 at Speyside, Tobago

When sea surface temperatures rise above the normal high for the year, it stresses corals causing them to expel the colorful algae that live inside the corals’ tissue and which provide the corals with their brilliant color and most of their energy needs. Bleached corals are weak and the longer they remain in this state, the more susceptible they become to infectious diseases and vulnerable to partial or complete mortality. Severe bleaching events often lead to significant decline in coral “cover” – the fraction of the reef covered by living corals — and changes in the average colony size. For instance, the average colony size declines as a result of partial mortality or fragmentation. Considering that larger corals tend to have greater reproductive output, a decline in abundance and mean size of coral colonies can greatly slow down the ability of the corals to reproduce, regrow, and thus recover following disturbances such as bleaching.

After witnessing the bleaching among the coral reefs that surround my home island of Tobago back in 2010, I decided to dedicate my Master’s thesis to studying the impact and recovery of these coral communities. With Simon Donner from the University of British Columbia and Jahson Alemu from the Trinidad and Tobago’s Institute of Marine Affairs, I examined changes in coral demographics over time (2010-2013) across three near-shore reef systems with different proximity to urban land. In addition, we tallied the juvenile corals at each reef, as their abundances are indicative of different species’ ability to reproduce sexually and survive. We also assessed sediment deposition and composition at each site using simple PVC pipe traps, as high levels of sedimentation are known to affect the growth stages in a coral’s life cycle. Continue reading

Can Canada live up to the promise of the Paris Climate Agreement?

My new article in Policy Options explores whether Canada can reconcile its climate policy targets with the temperature limits in the Paris Climate Agreement. The article is based on an analysis I conducted with Kirsten Zickfeld of Simon Fraser University – the report is available here.

The answer depends on how the world divides up the carbon that could be burned while keeping the planet within the temperature limits. From the report:

If you divide the pie based on each country’s present-day emissions, wealthy high-emitting Canada gets a generous helping for a country of its size (1.6-1.8% of the remaining carbon budget). If you divide the pie based on population, Canada gets a more equitable but much smaller slice (0.5% of the remaining budget).

With a generous helping of carbon pie, future emissions pathways for Canada that are consistent with the temperature limits would look like the figure at left. The 1.5°C limit is “at best unrealistic, at worst politically impossible.” The current Canadian target of reducing emissions by 30% below 2005 levels by 2030 could be consistent with the 2°C limit, provided emissions continue to rapidly decline after 2030.

Other countries, however, may not like Canada taking such a generous helping:

Allocating the remaining carbon budget based on present-day emissions places an unfair burden on developing and rapidly industrializing countries that historically have had low per-capita emissions. Despite being far less responsible for climate change to date, and currently having low per-capita emissions, countries like India would essentially be asked to bear an equal part of future mitigation efforts.

Equity, granted, is also an issue within Canada. I’ve been asked about emissions trajectories for individual provinces (that are consistent with the Paris temperature limits). Those trajectories would depend on assumptions about how Canada’s carbon budget “should” be allocated between different parts of the country. The answer for Canada as a whole is already dependent on assumptions about our slice of the global carbon pie; advancing this analysis to the provincial level would introduce even greater uncertainty, not to mention greater room for argument.

A simple approach would be to simply “scale” the emissions trajectories depicted above to the provincial emissions. Following that logic, the percent reduction targets, and the percent change in emissions by year, would be the same across all the provinces. That method, however, ignores the wide differences in mitigation potential and historic emissions burden. Perhaps the only thing that is clear from this analysis is that there’s no easy solution for Canada.



Oscars so white, planet not so white

In drawing attention to the urgency of addressing global warming during his acceptance speech, Oscar-winner Leonardo DiCaprio drew many cheers. He also drew a few rolled eyes in western Canada.

The film shoot for The Revenant did, as DiCaprio implied in his speech, actually relocate from Alberta due to a rapid change in weather and a lack of snow. The weather, though, was not much of a surprise to Albertans, or to any people who live on the leeward, inland side of a large mountain range.

It was an old-fashioned chinook caused by the difference in the rates that wet and dry air change temperature when forced to rise or fall over a mountain range. The same phenomenon is called a Wuhan in China, a Foehn in parts of Europe, and a Lyvas in Greece.

Naturally, DiCaprio’s speech pushed some buttons.

In scrutinizing DiCaprio’s claim, let’s not forget to see the forest – the climate – for the trees – the weather.

Whistler BC, March 2015

Last year absolutely whupped temperature records both globally, and in much of western Canada.  That was not your grandparents’ chinook: Calgary hit over 17°C, 4°C more than the previous record.  Temperature records were set that month on both sides of the Rockies. Snow depths hit record lows in parts of British Columbia. Ski areas struggled to stay open, or to keep enough snow to get to the bottom, as in this photo from Whistler, BC in early March.

DiCaprio’s speech about scouring the planet to find snow was broadly correct. Winters are getting shorter. It is getting hardeFig12-32r to find snow, particularly in late winter and spring. Since the late 1960s, Northern hemisphere snow cover has decreased 1.6% per decade in March and April and 12% (!) per decade (!) in June, according to the last IPCC report.

Snow cover is expected to continue to decline for decades into the future, especially if we continue doing business as usual. The graph shows the projected decline in March and April snow cover across the Northern Hemisphere under a variety of different climate scenarios, from the last IPCC report (the red scenario is roughly “business is usual”).

Leonardo DiCaprio’s example may not have been ideal. He may need to read up on adiabatic warming and cooling. Nevertheless, the planet is and has been getting less white.