h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

Hi, Willem

You wanted to see a cobra. If I had been along for the expedition,I would have been more interested in that mango tree and that cute frog. I'm not sure how sensible it was to eat in the shadow of a mango tree and eat termites. This would be like eating oatmeal in Beijing there you are, in the world's biggest rice-growing region, and you're not eating rice? And there you are under a mango tree, and mangoes don't tempt you?

Also, I am dismayed to learn that only 1 percent of South Africa has a forest cover.
http://www.theguardian.com/environment/2019/jul/04/planting-billions-trees-best-tackle-climate-crisis-scientists-canopy-emissions

If the world needs a trillion more trees, South Africa has the space for a lot of them.

I'm just sayin'.

Well, as it happens, I ate quite a lot of mangoes. There were millions of them just lying on the ground beneath the trees; most were actually still green, and the chickens rapidly got at the ripe ones, but I did get a few nice ripe ones and I ate them skin and all! Venda mangoes are delicious.

Well this whole tree thing has me a bit pulling out my hair. The thing is, South Africa despite having so little forest cover, already has too many trees, and few people can understand that. The majority of the country's natural vegetation is grassland. And … a heck of a lot of that has already been utterly destroyed by people planting trees on it! And not native trees … they plant mainly Australian eucalypts and Eurasian pine trees. These support little to no biodiversity. Whereas the grassland that had to make way for these plantations, supported staggering diversity. And with the grassland being planted with trees, we have actually lost species … not far from where I live there *was* a little lizard that lost all of its grassland habitat, now under pine and eucalypt trees. It hasn't been seen in decades and is likely extinct now.

What people also often don't realize, is that grassland also effectively store a lot of carbon, much of it below the surface in the form of bulbs, tubers, rhizomes, and even underground trees! And this carbon store is a bit 'safer' than carbon stored in trees, which are mainly above the ground - they can burn down and then a lot of the carbon goes back into the atmosphere. Whereas a grassland, when it burns, leaves most of the woody material untouched underground.

I am not actually against planting trees, BUT they must be the RIGHT KIND of trees and planted in the RIGHT PLACE. What we need more of is not forests per se, it is any and all kinds of truly natural environments. All of them store carbon, all of them are - if we let them be - resilient, all of them support great biodiversity and are part of the natural ecological balance which keeps the planet livable.

Beautifully explained, Willem! Thank you!

I do love forests. But they must be 'real' natural forests! The native forests we have here, rare as they are, are amazing and among my favorite places. Just a few dozen kms from my home town, there's the beautiful high-rainfall mist forests of Magoebaskloof. The trees are thick and gnarly but not particularly tall, and clothed in thick 'blankets' of mosses and lichens. There's a thick leaf litter supporting dense understory of ferns and a few shade-loving herbs and shrubs, and most of the trees have ferns and epiphytes like Streptocarpus and orchids growing on their trunks and branches. Calls of frogs, cicadas and forest birds resound with a kind of ventriloquial quality. There are fresh forest streams you can drink from, and beautiful waterfalls, some of the most fairytale-like being the 'tufa' falls where calcium carbonate precipitating from the water builds forward-growing 'terraces' below the falls.

Almost all 'real' forests in South Africa is currently being very strictly protected, because they are so rare. In terms of biodiversity, the forests are not as rich in species as most other habitats, but the species that do occur in them, mainly occur nowhere else. Forest birds include turacos, trogons, several species of bulbuls/brownbuls/greenbuls, thrushes and robin-chats. Forest mammals are bushpigs, duikers, Samango monkeys, and tree hyraxes (sadly not up here, but mainly along the coast). Our forests are not nearly as rich as the equatorial rainforests further up north.

Destruction of natural forests is a much bigger problem in many other African countries. Zimbabwe and Mozambique, our neighbour countries ... especially Mozambique, there is a forest region, the Haroni/Rusito which is a lowland forest, which hosts especially unique plant and animal diversity, which is being steadily 'eroded' to make way for people and farms. Much of Mozambique's forests are now being stripped of big trees by the Chinese. In equatorial Africa, rainforests are being cleared at a large rate, again to make way for burgeoning human populations. Equatorial West Africa has lost most of its rainforests already.

Again, beautifully put.

It has been said that before European settlement, a squirrel could climb a tree on the Atlantic coast, hop from one tree to another, and not have to set foot on ground until it reached the Mississippi. That's probably true. So people here associate settlement with forest loss, because the first thing a settler did was to 'clear' land. The good thing about these forests is that they can grow back - and they do, once people leave. Old field goes to forest, which follows its own timeline to 'terminal forest'. But not all ecosystems are the same, we tell them as we try to explain wetlands...

You know something I've noticed? No matter where you go, though, people who have always lived in one ecosystem have no clue how the others work. This is part of why we have problems with invasive species.

Take the asparagus fern - please. Used as an office plant in the Northeast. Most aggressive plant I've ever seen, and I've seen kudzu in the South. My Dutch/French/African colleague's asparagus fern kept wrapping its delicate tendrils around the light fixtures in the ceiling, no matter how many times she disentangled it. But it was no Audrey, and it couldn't survive outside in the snow.

Then I saw pictures from Florida - where asparagus ferns had grown up and destroyed houses.

http://www.gardenista.com/posts/gardening-101-asparagus-fern-houseplant/

http://plants.ifas.ufl.edu/plant-directory/asparagus-aethiopicus/

I grant you that I don't know which trees would be native to South Africa, and which ones wouldn't be. If I were involved, I would be very strict about the right species for the right places.

let's compare Scotland with South Africa. Scotland, which has about 13% forest cover (that's an old figure, so maybe it's different now), but it *probably* used to have many more trees. Scottish authorities would like to plant more trees, but the tourist industry objects. Plant trees, and people won't be able to see the heather, with the hills in the background.

Scotland has been occupied by people for a long time (mostly Caucasians, that is). South Africa was occupied for a long time, but nowadays the rest of the world is apt to talk about it as if things started when Europeans came down and settled it. I have probably erred by assuming that the Europeans did to South Africa what they did to Scotland -- cut down most of the trees. Maybe they didn't. My error. The world is a big place, and sometimes it's hard to grasp the nuances of a large part of it. )

Yeah Dmitri … over here we have a great variety of those Asparagus 'ferns' (they're not at all ferns actually, just asparagus plants, close relatives of the edible species) and in the veld over here, they are very humble and well-behaved. Take them out of their context, though …

I'm even know writing an article (partially) about this for a website …

Paulh, there are ways to check what kind of vegetation is more or less natural to an area. Plants and animals that are endemic to a region will have evolved there or close by … so the region must have been so as to allow them to survive there for sufficient time. Grasslands have lots of such local endemics, sometimes very old - both plants and animals - so the grasslands must be old also. The same is true of the fynbos shrubland of the south-western Cape.

In South Africa, humans have indeed been around for as long as they've been human, and have been using fire for a million years or more, but there's not much evidence of them transforming habitats on a large scale. Human populations have been low until indeed the Europeans came here. The 'oldest' indigenous populations, the Khoi-San, have had minimal impact, living as hunter-gatherers. Later immigrants from tropical Africa introduced more intensive livestock herding and agriculture, but they, too only had small impacts.


South Africa prior to European colonization was already a very dry country with few trees. The drought, generally, was what limited tree growth. More than half of the country gets less than 500 mm/20" of rainfall per year. Forests need at least 625 mm to grow in the cool winter-rainfall regions of the Cape, much more in the warmer summer-rainfall regions further to the north.

When the Europeans landed, they found a country that was open and 'empty'-looking. The Dutch when they arrived in the seventeenth century, found some forests in the Cape, and cut wood from them on a small scale, with only moderate deforestation resulting. The Brits came around the eighteenth century, saw all the open land and decided it would be much improved by lots of trees - so they planted them, trees from Britain and from their colonies in India and Australia, with the result of loss of great areas of shrubland and grassland, and several species of plant and animal.


Fire seems to have been a very long-term ecological factor, not much relating to humans. The most intense fires are in regions of high-rainfall grassland. These areas have rainfall that is enough to support forests, but the fires that burn in some cases every year, exclude trees. These fires mainly start as a result of lightning; very large numbers of plant species are adapted to regular fires, in fact needing these fires to stimulate flowering and the setting of seed. Fire cycles may vary from yearly fires, to fires at intervals of thirty years or so, and plants are adapted to specific regimens in different areas. Fynbos, often, has fairly infrequent fires ... but the fires do have to happen every decade or three, or else many species fail to propagate themselves by seed.

You can look at a rainfall map of South Africa, and check where rainfall is enough for forests ... these would already only be a few relatively small patches mainly in the south and east of the country ... but then those patches would also, mainly, be naturally under high-rainfall grassland, with regular extreme fires. On such grasslands, humans have now established lots of tree plantations, with fire control measures to protect them. Even the surviving patches of grassland are now becoming altered because of fire exclusion, with encroachment of trees and shrubs. And there is a big problem - unlike forest, which can re-establish itself if left alone, grasslands don't easily return after having been planted with trees. The entire soil structure is changed too much. If you leave a plantation alone after harvesting the trees, it doesn't turn back to grassland, instead it is invaded by a tangle of weeds and thorny shrubs.

In India, the Brits also considered grassland to be low-priority for conservation, considering them to be 'cleared forests'. We're now realizing that those grasslands must also be ancient, again on the basis of old endemic species being restricted to them - in the case of India the clue came from lizards.

Excellent points all! (And yeah, I don't know why we call that asparagus plant a 'fern', maybe to warn people they can't eat it? We have dumb people...)

There's been a lot of controversy in the US about fire suppression, too, in the West - and you've nailed it. One reason for that here is that people build expensive properties where they ought not, and then expect fire suppression to protect them, thus messing up ecosystems AND creating the danger of devastating fires when they do get started.

I know nothing about Australia's situation, but this current fire catastrophe is heartbreaking. At least it's finally beginning to rain.

I do wish that people tasked with educating the public would stop talking about 'climate change' in such a general way and start focusing on concrete issues. All anyone hears is 'go vegan' or 'drive a hybrid car' or 'buy my reusable tote bag', while missing down-to-earth (literally) issues of land and water management, development, etc, etc. It's enough to make a biologist scream.

My aunt is a biologist, and I'd rather *not* hear her scream . She's the one who scolded me for allowing a Japanese multiflora rose bush to grow next to my oil tank. Yeah, it was an invasive pest, but it was full of fragrant white roses every Spring, and the birds feasted on the rose hips in the Fall and Winter. I managed to get rid of it, but I'm not too happy with the dogwood that replaced it.

Dmitri, there's a huge problem. Actually, two huge problems. The first is … addressing the whole climate change challenge will have to involve many fields: actual climate science, but also biology, psychology, human culture, economics, philosophy, politics and even religion. Scientist in a very real way are not allowed to think or speak that broadly … they can't speak out of their particular field of expertise. So, the 'big picture' doesn't get looked at, holistic coping mechanisms aren't suggested. At least, not by actual scientists. Some 'big picture' folks who do suggest solutions may in turn not be qualified enough when it comes to the actual known scientific facts.

Which brings us to the second huge problem … at this very moment, millions upon millions of dollars are spent by the fossil fuel companies to try to deny or confuse the 'facts' (as they are known in science with a fair but not total degree of certainty). They use dirty psychological tricks similar to what were (and still are) used in propaganda wars such as the Cold War …

I can do a lot to speak about this issue, if I had the platform to do so … I try to see the whole picture and try to make sure of the actual science involved … but I'm just one person, and a limited one at that.

But anyways.

Paulh, there certainly must be, other than a dogwood, some nice fragrant floriferous shrubs that are native to your area and that would do well in a garden? What's so bad about that dogwood? We have a plant here called an African Dogwood, it's a very vigorous shrub (sometimes growing to tree size) with beautiful shiny leaves and red berries beloved by birds. It occurs in the shade of trees in savannah and forest and is a very easy plant for the garden.

I'm fond of dogwoods myself. Didn't know they'd grow up in Massachusetts, but then, I was surprised to see them here in Pennsylvania.

I agree, Willem: the situation needs a holistic approach.

A commentator yesterday mused that this 'climate change denial' is also, largely, 'science denial'. He speculated that a lot of people who were attracted to this view weren't good at science subjects in school, and thus liked to deny a scientific conclusion out of revenge.

To which I say that although I was very bad at abstract mathematics, I don't go around yelling that 2+2=whatever I feel like.

The dogwood wasn't flourishing in the spot I put it.I dug it u and put it in a large planter, where it has done well. It's more of a shrub than a tree.
http://www.missouribotanicalgarden.org/PlantFinder/PlantFinderDetails.aspx?taxonid=262959&isprofile=0&

dwarf red twig dogwood