I am a research scientist investigating the physiological responses of plants to water limitation. I am currently a Future Leader of African Independent Research (FLAIR) Fellow at the South African Environmental Observation Network. I completed my PhD at the University of Cape Town (South Africa) in 2014. My dissertation was an investigation into the role of plant hydraulics in determining the response of Fynbos to drought. After obtaining my PhD, I conducted postdoctoral research at the University of Tasmania (Australia) for two years. I examined the physiological factors that influence gas exchange in plant communities. I subsequently accepted a position as a post doctoral researcher at the University of California Berkeley (USA), examining fundamental questions in plant physiology and ecology.
In my spare time I enjoy appreciating nature, particularly interesting plants, and thinking about evolution. I think people benefit tremendously from having forests and natural plant communities to explore, and think we should do more to promote their conservation.
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Three months after I reported on a beached whale on South Africa’s south coast I ventured out to see if I could find any remains of the giant. A fine weather forecast and an early morning low spring tide (the first of 2022) provided the perfect opportunity to scan the coastline for any exposed bones, and thus we (me and some fellow nature enthusiasts) found ourselves heading out along the shoreline after a quick cup of coffee.
After walking for a couple of hours – and after passing many sand dunes and a river – we saw what looked to be a bone sticking out of the sand! So, we headed over to the spot and, sure enough! The first bone we encountered was a vertebra bone, and it was about the size of a medium size dog. We could also see several other bones scattered along the beach, most of them partially buried in the sand. We dug a few of them up and were struck by the size of the jaw bones and the scapula. Take a look at the size of this mandible!
Here is a video showing the scattering of what will soon become ashes along the beach:
Here are some of the bones with a dog for scale…
After a while we said our final goodbyes and ventured back along the beach. And so it is that another of life’s wondrous journey’s came to an end…
While on holiday in the Eastern Cape of South Africa, I stumbled across a dead humpback whale on the beach. I was immediately struck by…the smell of course (because it had been dead for a few days when I found it). Once I got over the olfactory shock I was impressed by the size of the creature! Take a look at this short clip of the moment I stumbled across it:
In the photograph below you can clearly see that it is lying on its back:
According to wikipedia:
“The humpback whale (Megaptera novaeangliae) is a species of baleen whale. It is one of the larger rorqual species, with adults ranging in length from 12–16 m and weighing around 25–30 t. The humpback has a distinctive body shape, with long pectoral fins and a knobbly head.”
I estimated the humpback whale on the beach to be approximately 12m, and I was indeed struck by the length of the pectoral fins. Take a look at the size of these fins!
I am not certain what killed the whale, although it could possibly have been hit by a large ship or vessel. According to wikipedia again these magnificent cetaceans travel long distances to get to their feeding or breeding grounds.
“Found in oceans and seas around the world, humpback whales typically migrate up to 25,000 km (16,000 mi) each year. They feed in polar waters, and migrate to tropical or subtropical waters to breed and give birth, fasting and living off their fat reserves. Their diet consists mostly of krill and small fish. Humpbacks have a diverse repertoire of feeding methods, including the bubble net technique.”
Below, you can clearly also see the baleen that they use to filter their tiny prey. The dense hair reminded me of porcupine quills, while the inside structure was like a plastic accordian (though it’s made of keratin in the whale).
In the past, the humpback whale was a target for the whaling industry and the species was once hunted to the brink of extinction (like several other whales). According to wikipedia, the population of humpback whales “fell by an estimated 90% before a 1966 moratorium”. Since then the number of humpback whales has “partially recovered to some 80,000 animals worldwide”, but entanglement in fishing gear, collisions with ships and noise pollution continue to affect the species”. Although I did not notice any obvious injury to the whale, it was on its back, so I could not tell whether it had been hit by a ship or not.
As for why whales get so big? My guess is that there are at least two reasons. Firstly, creatures living in water can grow larger because their bones do not have to support as much weight as land mammals living in less buoyant air. Secondly, because water conducts heat away from the body much quicker than air (air is a good insulator), the animals must generate significant fat reserves to maintain their body temperature. A large body also increases the ratio of the internal volume to the surface area, which serves to further reduce heat loss. You do not find many mice-sized mammals living permanently in the ocean!
I posed this question to the Thicket Forum; a virtual conference celebrating the wonderfully diverse Subtropical Thicket biome in Southern Africa hosted by Alastair Potts of the Nelson Mandela University. Take a look and decide for yourself:
I recently put together a presentation of my research work for the SAEON seminar series – monthly presentations across the SAEON nodes – in which I argued the case for investing in whole-plant physiology research (You can find the video at this link, and I hope it is worth a watch!). My reasoning is as follows: 1. The natural world provides almost infinite services for us (and other life forms, of course). Some of these “services” are fairly easily quantified, while others are very difficult to quantify. For example, it might be possible to quantify the health benefits of clean drinking water or the volumes of water running off of a mountain catchment area, but how do we put a monetary value on improved human psychology resulting from a sense of place, wonder, awe or calmness that many get from healthy, natural places? 2. The world is changing in several ways at remarkable rates, and this will impact life on the planet. Humans and our tools are an incredibly powerful force in driving some of this change, including our propensity to dig up and burn fossil fuels, which is leading to increased global temperatures and other changes to the climate. I am beginning to think of our actions as being part of a kind of unplanned global experiment… 3. Species respond differently to such global changes. In the talk I provide several examples of where we have observed different responses among co-existing species to changes in one variable – rainfall – in Southern African ecosystems. 4. There is an urgent need to better understand these species-specific impacts if we are to understand and predict the outcomes of our global experiment. And if you are involved in policy or industry, a fifth point might be to act upon this knowledge as it comes in.
Does environmentalism need a re-think? And if so, why?
Now, this all seems fairly obvious and straightforward to me (and to those involved in conservation work, I gather), but I often wonder what is preventing us from making more progress in the realm of environmentalism. I can put forward two possible answers to this problem: The first is that the first two points in the line of reasoning may not be evident to most people. I suspect that we (i.e. humanity) have not fully grasped the point that we are entirely dependent on and immersed in the natural world. I would suggest reading E.O. Wilson’s Biophilia or Consilience, both excellent books illustrating our reliance on the environment, to gain deeper insight into the nature of our dependency.
The second answer is that we are locked into ways of living that preclude us from acting on our knowledge. If this is true, I wonder if being “locked in” is simply a failure of imagination on our behalf to generate alternative means of income, or whether there is something more to this. We get clean drinking water from healthy rivers, but this does not provide us with apples and gold or platinum…all of which might be essential. Another way of phrasing this is to say that there might simply be too many of us to exist in a sustainable manner. I can remember engaging with a website that calculated how many earth’s would be required to support my lifestyle if everyone adopted the same level of consumption, and the result was something close to 2 and a half earth’s. I wondered what it would take to cut this down to 1 planet earth; what sacrifices would I need to make to my lifestyle and were these possible? I think the answer is yes, but, again, it might take some imagination.
South African plants are set to receive their share of the limelight! A new television series will uncover the secrets of our indigenous flora, by describing stories of plant evolution and diversity! I can’t wait to tune in, especially because the first episode is on Fynbos.
WARNING! High species diversity ahead! I recently travelled to the South Africa’s Eastern Cape Province to conduct some field work with Daniel Buttner and Alastair Potts of the Nelson Mandela University in Port Elizabeth (Alastair is an ecologist and lecturer and Daniel is a postgraduate student in the Botany Department at NMU). The trip has involved working in some of the most remarkable plant communities, or biomes. You can think of a biome as a type of close-knit community of many different species interacting more closely with one another than with species from other biomes. For example, types of temperate forest or mangrove forest are different biomes. What is remarkable about the biomes of the Eastern Cape is that they are often found in very close proximity to one another. One small reserve that we travelled to contained about six different biomes, meaning that there were six different plant communities all operating independently but with very sharp boundaries between them! This results in an incredibly rich diversity of plants in a very small region, all doing slightly different things. The edges of the biomes (also known as biome boundaries) are controlled mostly by soil type, fire and climate.
Perhaps the most unusual of these biomes is the Thicket Biome, consisting of stunted (low growing) trees and succulents. The plants of the Thicket Biome are incredibly dense (as the name suggests), and also often spiny, so it is hard work making ones way through a patch!
WARNING! Distressing images of stressed trees ahead! The goal of the trip was to assist Daniel in quantifying water stress levels of Pappeacapensis trees, to help determine how severely impacted they are by the current drought in the region. It has been very hot and dry for several months and many of the plants are showing visible signs of distress or have died (although it is currently raining as I type this!).
In addition to the obvious signs of distressed plants (and on a more positive note) I have been most impressed with the diversity of plants and growth forms in the area. It is wonderful to see an abundance of succulents and low growing trees, and even patches of fynbos most commonly associated with the Western Cape Province growing high up on sandstone-derived soils. It was also my first time experiencing a cycad forest, which (as Daniel noted) felt a bit like walking through Jurassic Park! Some areas even had cycads growing next to fynbos species.
In light of the upcoming Heritage Day in South Africa (September 24th), I decided to celebrate an element of our heritage that I find interesting, namely the excursions and encounters of some of the early British explorers. In the early 1800s the British were interested in expanding their influence around the world, including in Southern Africa, and a part of this endeavor was sending naturalists and explorers to collect information on the land, it’s people as well as on the local animals and plants. William John Burchell was one of these naturalists who has gripped my attention because of his fascinating character and because his exploration, discoveries, plant and animal collections and field notes have increased the knowledge of subsequent generations.
Burchell travelled to South Africa in 1810, arriving in the Cape of Good Hope in November 1810, and spent the next three years exploring the Cape, the broader Colony and the land beyond the borders of the area colonised by people of European descent at the time. His travels were undertaken for the purpose of “acquiring knowledge” of Southern Africa, including the local flora and fauna, as well as suitable areas to settle. In years following his time in Southern Africa, Burchell published a very detailed account of his travels in two volumes of his famous journal, Travels in the Interior of Southern Africa (see the title page above). I have read both volumes and found them highly engaging; full of fascinating details about life in Southern Africa at the time. For example, Burchell’s notes describe some of the plant species that he came across, including several species that were unknown to European naturalists at the time:
In addition to the extensive notes on natural history contained within the journal, Burchell also published a map and made hundreds of sketches. Some of these sketches were published in the journal in the form of woodcut vignettes, adorning the headings or end of the chapters. Now, before embarking on the long expedition throughout Southern Africa, Burchell explored the Cape region in a few local trips. Two of the vignettes in his Travels depict scenes from a short journey that Burchell undertook to Tulbagh, a small farming town located about 120 km from Cape Town (see map). I was intrigued to figure out whether I could reproduce some of the scenes, so I undertook a similar journey (not in an ox-wagon) to see what I could find.
Two of the scenes from Tulbagh depict the Drostdy and the main street in the Village. About the former Burchell wrote: “At a distance of half an hour’s walk northwards from the village is the Drostdy. This is a large and handsome stuccoed building, ornamented in front with a portico of three arches, to which the ascent is by a flight of steps. It contains several large and lofty rooms, together with a spacious council-room in which public meetings and the sittings of the judges at the annual circuit are held.”
I managed to place myself in almost the precise location that Burchell must have stood, although the trees have grown a bit since he drew it! In addition to the ravages of time, the Drostdy has survived a fire (in 1938) and an earthquake (in 1969). Part of the building has been restored, although I am not certain which bits are the original…so the restorer has done an impressive job.
The village scene was slightly more difficult to pinpoint, although still not terribly difficult because Burchell’s notes made it clear where he stood: “The village, as viewed from the parsonage-house, and looking southward.” A couple of things have changed in the intervening 210 years: The “row of young oaks along the street” have become much older and taller, obscuring the “mountains in the distance” (which Burchell referred to as the Roodezands Kloof, but I think they are the Witzenberg mountains?), and the mode of transport has also advanced. But nevertheless it is remarkable how little time seems to have changed the village:
I quite enjoyed stepping back in time, and found it quite engaging to place myself in the footsteps of Burchell. Doing so seems an appropriate way for me to celebrate my South African heritage, although the British explorers are, of course, only a small part of the wonderful, rich cultural heritage of the people of this great country.
Spring has sprung in the southern hemisphere, although you wouldn’t believe it in Cape Town at the moment because it’s raining and cold. But, more to the point, this means that Arbor Week has begun! Arbor Week is usually associated with planting trees: I fondly remember planting young saplings at my school when I was younger. Although tree planting is something to be celebrated, trees are not the only type of plant that we should be planting. This is because trees do not occur in all environments (e.g. South Africa’s grassland areas or parts of the Succulent Karoo) and because trees are only one type of plant.
Take cycads, for example: cycads are seed plants (like conifers and flowering plants) with a very long fossil history spanning about 200 million years! Individual plants typically have a stout and woody trunk with a crown of large, fairly tough, evergreen pinnate leaves (like the individual above). Cycads were formerly more abundant and more diverse than they are today; their “hey-day” occurred during the Late Triassic or early Cretaceous epochs. Sadly, these unusual plants are threatened with extinction today, with many of the species having highly restricted geographic ranges and low population sizes. One species (Encephalartos woodii) is known to have only a few male individuals left, so is unable to reproduce sexually.
This year I am trying to cultivate a diverse range of plants, including cycads and restios. A friend of mine was kind enough to donate some seeds from an Encephalartos individual that is growing in his garden, and I was able to purchase some restio seeds from a local supplier. Let’s hope conditions get a little warmer in Cape Town, so they can germinate!
The Western Leopard Toad is an endangered species (according to the IUCN) found mainly in sandy coastal lowlands in two disjunct areas of the Western Cape of South Africa: one close to Cape Town and another in the Overberg region. In those areas the toads live in gardens or in coastal lowland flats, but also in the adjoining valleys and mountain slopes. Every year the toads migrate toward local water bodies from the surrounding areas to breed, and this usually occurs in August after rain. Well, the toads are on the March at the moment!
Their biology is quite interesting. In addition to the annual migration to water bodies, apparently they can live for up to 14 years and reach a size of 14cm in length! That’s quite a toad! They also eat snails and small insects.
My wife and I consider it fortunate that a few resident toads live in our garden, where we often hear them croaking away. However, at the moment their croaks are being drowned out by the chorus of the migrants!
Every year the semi-arid and usually quite drab West Coast of South Africa becomes a carpet of flowers. This generally occurs in late Winter or early Spring (i.e. from mid August to early September) following the rainy season. Along the West Coast winters are generally mild and fairly wet in the south west, but conditions get drier as one moves further north toward Namibia. The flowers are especially prolific during years with higher rainfall. Because the West Coast has received very good rainfall this year, my wife and I decided to take a trip to see the show for ourselves. We drove to the West Coast National Park (about 2 hours drive from Cape Town) and were certainly not disappointed: the flowers are magnificent this year. There were several areas with standing water, indicating how good the rains have been (such as this pool, below) and carpets of red, orange, white pink and yellow flowers.
Annual plants, such as these daisies (above), are especially spectacular and are the stars of the show. I think most of the species are in the genus Arctotis, although daisies like these are notoriously difficult to tell apart (if anyone has a better identification please let me know in the comments). These plants tend to be herbaceous annuals that grow quickly, produce flimsy leaves and shallow roots with large flowers and survive most of the year (when the soils are dry) as seeds.
However, quite a few perennials (such as mesembs and Euphorbia below) also produce flowers during this time. Many of these plants tend to be succulents, surviving through the drier times of the year by relying on internal stored water.
Mesembs and Euphorbs are also notoriously difficult to tell apart, so I am not certain of these species either. However, I think most of the mesembs (also locally known as “vygies” because of the fig-like fruits that these species produce) are of the genus Lampranthus. I also think that the species below might be Euphorbia burmannii, because it is intricately branched and lacks the false flowers that I associate with Euphorbia mauritanica, a similar-looking species that is also widespread along the West Coast.
Not all succulent species flower with the rainy season. These species rely on stored water to produce flowers later in the season. One benefit to delaying flowering is that pollinators might be less distracted by the showy annuals!
Here is the wonderfully-named Euphorbia caput-medusae, which was locally common in the Rocherpan Nature Reserve (which I highly recommend to anyone planning a trip along this coast).
There were even a few parasitic plants, like this Cytinus sanguineus (below), which is a root parasite that has no leaves. The species has been placed in Rafflesiaceae, the same family as Rafflesia arnoldii – the species with the largest flower – but I think that the classification is uncertain at present (if anyone knows differently please let us know in the comments). I am not entirely certain why this species would be flowering now if avoiding competition for pollinators is highly important.
I must admit that even though flowers are not everything that there is to a plant, the allure of the annuals’ display is very hard to resist.