Can coral reefs recover from bleaching? The case of Tobago

Posted on by
1

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 →

The Vancouver Climate Agreement

Posted on by
Reply

This week, the students in my course “Climate Change: Science and Society” completed the “22nd” Conference of the Parties to the UN Framework Convention on Climate Change (UNFCCC). Groups of students representing 24 different countries worked feverishly for a week to complete an agreement. Without further ado, we present to you the Vancouver Climate Agreement:

VANCOUVER CLIMATE AGREEMENT

OUTCOME OF THE MOCK 22nd CONFERENCE OF THE PARTIES TO THE
UNITED NATIONS FRAMEWORK CONVENTION ON CLIMATE CHANGE

1. All countries present agree that forests, land use changes, and other sinks shall be included when calculating net greenhouse gas emissions, excluding unintentional and unavoidable natural disasters such as pests and fires. Greenhouse gas emissions including emissions from land use, land use change, and forestry should be reported every five years. Continue reading →

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

Posted on by
Reply

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.

 

 

Canada’s contribution to meeting the Paris temperature targets

Posted on by
Reply
PM Trudeau in Paris (CBC)

PM Trudeau in Paris (CBC)

At this week’s First Ministers’ Meeting here in Vancouver, the federal government begins the politically difficult task of establishing a national climate policy. The first step is coordinating the existing patchwork of provincial policies and carbon pricing systems.

Underlying this conversation is a question that has remained unanswered since Canada’s much-celebrated turn at the 2015 United Nations climate summit in Paris:

Are the existing or proposed national emissions targets consistent with the global promises made in Paris?

Together with Kirsten Zickfeld of Simon Fraser University, I completed a report on future CO2 emissions trajectories for Canada that are consistent with avoiding the global temperature limits in the Paris Climate Agreement.

The analysis in our report suggests that the current Canadian target of a 30% reduction below 2005 levels by 2030 could be consistent with maintaining a likely chance (66%) of limiting warming to less than 2°C globally, but only if Canada is given a generous allocation of the world’s “remaining” future carbon budget (based on the present fraction of the world’s emissions). A target consistent with a likely (66%) chance of avoiding 1.5°C of warming globally is extremely limited regardless of the method of allocation. Even under a generous allocation to Canada, national net CO2 emissions would need to decline 90-99% below 2005 levels by 2030.

For more, see the full report available here. I’ll also write more on this subject in the coming weeks.

 

 

 

Oscars so white, planet not so white

Posted on by
Reply

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.