The Tortoise and the Hare – The story of two Trees

Why are large milkwood trees so scarce in Cape St Francis?

An article on Milkwood’s by Prof Richard Cowling

Think of the Cape coast and what tree springs to mind? For most, it would be the white milkwood tree (Sideroxylon inerme). From Kommetjie on the Cape Peninsula to the shores of Algoa Bay and beyond, dune thickets and forests are invariably dominated by milkwood trees. Yet this is not the case here in Cape St Francis where kershout (Pterocelastrus tricuspidatus) is the most conspicuous denizen of our dune thickets. Why is this so?  

Kershout (left) and milkwood (right).

Kershout (left) and milkwood (right). Note the distinctive orange fruits and oval-shaped leaves of kershout. Milkwood has leaves with prominent veins that produce milky sap when detached from the branch.

The answer is simple – fire. Let me explain.

Kershout is better adapted to fire than milkwood. It is capable of resprouting vigorously after fire.

Every plant that we monitored after the fierce fire of January 2016 resprouted from buds at the base of the plant. On the other hand, almost 20% of milkwoods were killed outright by that fire and those that did survive also resprouted from basal buds, but at a much slower rate than the kershout.

Kershout (left) resprouting

Kershout (left) resprouting vigorously 16 months after the January 2016 fire in Cape St Francis. At the same time, milkwood (right) had produced far fewer sprouts.

A key feature of kershout’s ability to tolerate fire by strong resprouting, is that mature plants are multi-stemmed. This enables the plant to rapidly occupy space in the postfire environment and outcompete more slower growing plants such as milkwood – hence the hare (kershout) and the tortoise (milkwood).

Mature kershout

Mature kershout (left) and milkwood (right) trees in dune forest. Note the multi-stemmed kershout with its numerous, almost vertical stems and dense canopy shading out any competitors. Milkwood, on the other hand, has few basal stems and grows much taller and spreads more widely than kershout.

 But, as in everything in nature, every strategy adopted by a species has implications. The cost to kershout of investing so many resources in all those stems is a limited height. Imagine, in the photo below of a mature, multi-stemmed kershout, if all that wood was allocated to a single stem: the plant would be three times its present height!

Thus, the hare (kershout), while rapidly occupying space by strong post-fire sprouting, is – in the long-term (more than 50 years at least) – outcompeted by the taller and more widely spreading canopy of milkwood (the tortoise), which overtops the kershout, denying it light.

We can conclude then, that dune thickets and forest dominated by kershout have been subjected to relatively frequent fire whereas those dominated by milkwood have been fire-free for centuries or more.

Here in Cape St Francis, our dune landscapes have likely been swept by fierce fires driven by the frequent westerly gales that the area experiences. This fire regime has benefitted kershout at the expense of milkwood. Only in Seal Bay nature reserve, tucked as it is in the corner of the bay and thus protected from the wind-driven fire path to the north, do we find mature milkwoods.

The warmer and drier conditions predicted for our region because of human-induced climate change will likely result in a higher frequency of intense wildfires. These conditions will favour the fire-loving kershout and limit the prevalence of the iconic milkwood, which will remain dominant only in sites that free from even the wildest of veld fires. Such is the fate of the tortoise in the rapidly changing world of today.

ancient milkwood

An ancient milkwood killed by an unusually intense wildfire that burnt through dune forest at Franskraal near GanBay in the Cape

Maya Gabeira Sets New World Record, Wins cbdMD XXL Biggest Wave Award 

 Yesterday, the World Surf League (WSL) announced that Maya Gabeira (Rio de Janeiro, Brazil) won the cbdMD XXL Biggest Wave Award and set the new World Record for the largest wave ever surfed by a woman. As part of the Red Bull Big Wave Awards (BWA), the BWA validated Gabeira’s ride as the new GUINNESS WORLD RECORDS™ title holder for the largest wave surfed (unlimited) – female.

“This wave was during the [WSL Nazaré Tow Surfing] contest and although I say I’m not a competitive person, I was very in the zone and braver than I usually am on this day,” said Gabeira. “I was risking more than I usually like to do. When I let go of the rope, I had a feeling it could be the one but wasn’t sure. The speed was very high but the noise that the wave made when it broke made me realize that this was probably the biggest wave I’d ever ridden.”

Gabeira’s record-setting wave measured 73.5 feet, besting her own previous World Record, 68 feet. She broke the record at the infamous big-wave surf break, Praia do Norte in Nazaré, Portugal, on February 11, 2020, as part of the WSL’s inaugural Nazaré Tow Surfing Challenge event. Although the men’s and women’s divisions are separate for this category, Gabeira’s ride also beat the men’s cbdMD XXL Biggest Wave, which was won by Kai Lenny (Paia, Hawaii) and measured 70 feet. 

“This World Record really strikes me as quite amazing because the size of the wave was measured taller than the men’s size for the winner, so it means a woman actually rode the biggest wave of the year overall,” continued Gabeira. “That to me was something I had dreamed of years ago but not as something realistic. There was no representation for me to believe that it was possible but to see that happen is incredible. This is seen as an extremely male-dominated sport, so to have a woman be able to represent that is quite rare.”

In one of BWA history’s closest races, Gabeira’s ride measured only 2-to-3 feet larger than Justine Dupont’s nominated wave from the same competition day on February 11. Dupont’s second nominated wave took place on November 13, 2019, also in Nazaré, Portugal.

“I am a big fan of Justine (Dupont) and what she has been doing at Nazaré,” said Gabeira. “I think it’s one of the reasons I kept pushing myself. I was on the edge of retiring a few years ago and then I saw her evolution and thought I have to keep up for a few more years. I really didn’t expect to go any bigger or anything like that, but I kept riding and enjoying my time at Nazaré and that wave was quite special although it was quite terrifying as well.”

Justine Dupont Wins Ride of the Year and Performance of the Year Awards

Despite measuring only a few feet shy of the 2020 cbdMD XXL Biggest Wave Award and the World Record, Dupont celebrates an incredible season with wins in the Ride of the Year and Performance of the Year categories. Dupont, the 29-year-old from Seignosse, France, is one of the most decorated women in big-wave history and will continue to push the boundaries of big wave surfing.

“This wave was really special and every one said to me that this wave was really special from the shape to the footage, all the angles, and the size,” said Dupont. “Everything made this wave special and having all the community speaking about it like this was a big reward. It is not about a performance for a woman but a performance for a surfer. Having Kai (Lenny) and Lucas (Chianca), the best in the discipline, wanting to surf this wave, and I was on it, so I am really stoked. This wave is special so having the Ride of the Year means I had the best line possible on a giant wave and I made it.”

 

The rides submitted for the women’s cbdMD XXL Biggest Wave Award by Dupont and Gabeira were incredibly close and a potential World Record. As such, WSL deemed it important to have the data reviewed by an independent scientific team as a critical point of reference for the determination of the biggest wave. The team included members from the WaveCo Science team, the Scripps Institution of Oceanography, and the University of Southern California, Department of Aerospace and Mechanical Engineering. 

The analysis was based on video and photo imagery, camera locations, camera lens parameters, and environmental conditions, including tides, sunlight, and wave set-up. Collinearity equations were used to transform the image coordinates into real-world coordinates based on estimates of the geometric parameters, including the height of the cliff at Nazaré. In addition, fixed reference points in the imagery, including the surfers’ heights, surfboard and jet ski dimensions, and estimated crouching heights, were utilized in the scientific calculations. 

Red Bull Big Wave Awards Congratulate All 2020 Winners
The 2020 Red Bull Big Wave Awards will officially close today after celebrating the best in big wave surfing over the past year. Every wave ridden at every big wave break around the world in this period was eligible for consideration across five award categories: Ride of the Year, cbdMD XXL Biggest Wave, Performance of the Year, Biggest Paddle of the Year, and Wipeout of the Year. 

Experience all winning rides and highlights from the Red Bull Big Wave Awards at WorldSurfLeague.com/BigWaveAwards

RIDE OF THE YEAR
Justine Dupont (Seignosse, France) at Nazaré, Leiria, Portugal on February 11, 2020
Billy Kemper  (Haiku, Hawaii) at Jaws, Maui, Hawaii on January 23, 2020

cbdMD XXL Biggest Wave
Maya Gabeira (Rio de Janeiro, Brazil) at Nazaré, Leiria, Portugal on February 11, 2020
Kai Lenny (Paia, Hawaii) at Nazaré, Leiria, Portugal on February 11, 2020

PERFORMANCE OF THE YEAR
Justine Dupont (Seignosse, France)
Kai Lenny (Paia, Hawaii)

BIGGEST PADDLE OF THE YEAR
Paige Alms (Haiku, Hawaii) at Jaws, Maui, Hawaii on December 12, 2019
Eli Olson (Haleiwa, Hawaii) at Jaws, Maui, Hawaii on December 12, 2019

WIPEOUT OF THE YEAR
Keala Kennelly (Honolulu, Hawaii) at Jaws, Maui, Hawaii on December 12, 2019

The 2020 Red Bull Big Wave Awards are proudly supported by Red Bull and cbdMD.

For more information, please visit WorldSurfLeague.com.