Jottings about trees

Autumn in a Mount Wilson (NSW, Australia) garden: you can see (L to R) cyprus, birch, Japanese maple, eucalypts, deodar, cherry laurel

Most people take trees for granted: they’re those large plants with big hard stems and leafy tops. Even those who live in cities and virtually never see a tree except in parks, know that different types (species) vary enormously in size and structure. Also, everyone knows – vaguely, in some cases – that there are different forest types, although  most would be a bit pushed to name some, or to describe the basic characteristics of, for example, coniferous, tropical or temperate deciduous forests.  None of which is particularly important; lots of people have a very strong aesthetic appreciation of the beauty of trees and forests, and probably recognise, at least instinctively, that they are very important in the world, even if that recognition is confined to the knowledge that wood comes from trees and that paper is made from wood. And the modern world uses a great deal of paper.

Eucalyptus plantation in Brazil. A forest farming operation; the world uses a lot of paper.

Trees in African savannah

Trees and forests feature quite largely in poetry and literature. As kids we were probably absorbed by Grimm’s fairytales, which tend to feature dark forests (they were written in northern Europe where many of the forests are coniferous and dark). And of course dark forests feature in Nordic myths and legends, not to mention Robin Hood and Lord of the Rings. Then there was Enid Blyton’s “The Faraway Tree” and, in modern adult literature, Eucalyptus, by Murray Bail. Last Christmas my family gave me a book of beautiful photographs of, and comments on, Australia’s remarkable trees (Richard Allen and Kimball Baker): they range from the gnarled and twisted acacias surviving improbably in arid semi-deserts to towering, majestic karri in Western Australia and (the misnamed) Mountain Ash (Eucalyptus regnans) in Victoria and Tasmania. You could probably find references to trees in Shakespeare’s plays, but I have to confess that I’m not familiar enough with those to be able to say where, at least not ‘off the cuff’.

Big trees, when you think about it, are amazing. That whole massive structure consists of microscopic cells, of a range of specialist types doing different jobs: cells in leaves doing photosynthesis – breaking down CO₂ to produce the carbohydrates that underpin all (or nearly all) life on earth; nutrient absorbing cells in the roots; cells that transport nutrients and water up the trunk and structural cells that determine the shape and strength of the tree.

Across the road from my office I can see tall, straight eucalyptus trees in my neighbour’s garden. They’re about 30 m high, with slim white trunks. The branches and foliage are mostly in the top half – in fact mostly in the top 10 m, so when the wind is strong the force (drag) on all that material stuck up in the air is enormous. (I once spent several interesting weeks in a wind tunnel measuring the forces on trees and their foliage elements.) But, regardless of the technicalities, the practical result, for my tall neighbours, is that their tops swing through arcs that I estimate must be at least 5 m. It can be quite alarming: as gusts ease the tops swing back, to be driven out again by the next gust. And the trunks don’t break. It’s only in recent times that humans have been able to make materials (using carbon fibre technology) that would stand that amount of flexing.

Not that trees never break; they do, of course, and they also get uprooted in high winds. Breakage or uprooting happens when the frequency of the gusts matches the way the trees flex (their natural elasticity) so that the trunks swing more and more with each gust and eventually reach their limit. (This doesn’t just apply to trees; it can happen to tall man-made structures. An astonishing example was the collapse of the Tacoma Narrows suspension bridge in Washington State in 1940. The so-called structural frequency and elasticity of the bridge were freakishly matched by the gust frequency of a strong wind and the structure was spectacularly destroyed.

A unique hotel in Ecuadorian rainforest

It’s a sad fact that forests, particularly tropical forests, are being destroyed around the world – particularly in Indonesia, Papua New Guinea, the Pacific islands and the Amazon Basin – at an alarming rate. The destruction is driven by human greed and short-sightedness (why are we not surprised!?) to provide hardwoods, land for palm oil plantations and soya bean production and ever more space for the encroachment of peasant farmers. This has huge implications for biodiversity, hydrology – affecting river flows and, when the clearance is on a large scale, local climates – and for the carbon balance of the world as a whole. Forests absorb enormous quantities of CO₂ and store massive amounts of carbon. When they are destroyed most of that carbon is released into the atmosphere, contributing to the increase in atmospheric CO₂ being driven by the combustion of fossil fuels.

So it’s worth getting political about trees and forests and trying to persuade politicians that they are important in the great scheme of things which, as far as I am concerned, means the health and beauty of the planet.

Okavango

Okavango

The Okavango Delta is formed by a river coming down from the Highlands of Angola, which disappears into the deserts of north-east of Botswana, creating an inland delta. There are a few other such deltas in the world, but the Okavango seems to be one of the most remarkable and best-known examples. Flows vary seasonally and the water is crystal clear, filtered by the huge areas of reeds, papyrus, sedges and grass, and waterlilies (water hyacinth), through which wind multiple channels, many made by hippos. The area, along its borders and on the numerous bush-covered island, is home to a wonderful range of African wildlife.

Impala rams watching a lion. Once they have spotted the predators they're pretty safe

Male cheetah

Not all the wildlife are large: Diana and chameleon

Botswana itself is widely regarded as the most successful African state, although it’s a very small country with only about 1.4 million inhabitants. However, it has a functioning democracy and a government which appears to govern for the good of the country and not just for the good of the members of the government, as is the case in most African states. The towns are extremely scruffy and untidy, with rubbish all over the place – their priorities are different from those of most westerners – but the country is moderately wealthy with important diamond mines, a major beef cattle industry and a thriving tourist industry. I don’t know much about tax structures and agreements between governments and extractive industries, but it’s clear that, unlike the oil industry in various countries, the diamond mines in Botswana pay enough to the country to benefit everyone and not just the companies doing the mining. Tourism is what’s called “low-volume”, which really means that Botswana is generally too expensive for student backpackers and young people on limited budgets, since it involves guided safari-type tours with small groups who may camp out – in reasonable comfort, but it is camping in the African bush - or who may lodge in safari camps.

Diana and I went to southern Botswana, to the Kalahari, a few years ago, and a few weeks ago we went to the Okavango, where we spent four days in two separate camps, one of which is fly-in access only. From the first camp, Khawai River, reached in about four hours across fairly rough roads from the town of Maun, we went on a number of game drives (the name tells you something!) in safari vehicles which bumped or crawled slowly along bush tracks in the area east of the Moremi Reserve. I must admit that we sometimes wondered about those tracks: the main, established ones are clearly identifiable, but although we were told that the guides – who were also the drivers – were not supposed to go into the bush they frequently did so, and when they did the vehicles created the beginnings of a new track. As a result the area, which is very wet at the moment, is criss-crossed by networks of minor tracks. This, over time, constitutes a lot of damage, but since the vehicles and guides responsible come from a number of companies, and the area is remote, it is very difficult to prevent.

Elephant at 10 metres

Safari vehicles  - generally long-wheel-base 4WD vehicles, open-backed with a couple of rows of tiered seats – are not comfortable, but they’re not too bad and ours were never crowded; a maximum of six people to a the vehicle that could carry nine. The guides were very experienced; experts at finding animals about which they generally knew a great deal. In a few days we saw hundreds of elephants, probably thousands of impala, a leopard (rare sight in daytime), lion, serval, cheetah, a couple brown hyenas, a hippo wandering around in broad daylight as well as a number of hippos in the rivers, zebra (with young), giraffe (also with young), kudu and various birds. Impala have black markings on their hindquarters that look a bit like the big M symbol of the Macdonalds fast food chain. Our guide observed that this was probably appropriate as the poor impala are on the menu of all the predators – lion,  leopard, cheetah, hyena (which can sometimes catch them at night). Fast food in every sense! We sometimes saw animals very close-up so the game drives were extremely satisfying and sometimes quite exciting.

Xaxaba Transit lounge

We flew in a small aircraft from Khawai River to Eagle Island. From there we went on several boat trips in flat-bottomed boats with outboard motors; again driven by guides who knew a great deal about the Delta and its fauna. Although the birdlife is not hugely prolific–you don’t see great flocks of birds–we saw fish eagles, Jacana, or lily trotters, otherwise known as Jesus birds because they appear to walk on water, and various sorts of duck and kingfisher. There were frequent sightings of hippo, usually submerged with just the eyes and nostrils sticking out of the water, sometimes half the head but occasionally, in  the evening, heaving themselves out of the water. At one point we had to pass quite close to a group of hippo in the main channel. Our guide, John, was wary of them as he knew that they may resent the boat and that they could be dangerous. He gunned the motor past the hippos and was proved to be correct when one of them set off after us, showing an astonishing turn of speed for such a huge animal. Hippos apparently do not swim so the hippo chasing the boat was presumably running in the water although he was lifted slightly out of it in doing so. You certainly would not have wanted to be in a canoe at that point.

Intruder in camp - or maybe we're the intruders

There was also some excitement in the very comfortable camp, where there was a large marula tree, a species that produces fruit highly attractive to elephants, especially when they (the fruit – not the elephant) are slightly fermented. A large bull elephant came to feed on the marulas on the couple of nights when we were there: on the second morning he was right next to the path between the huts. One of our group needed to walk past him to fetch something so  - as advised - he asked John to come with him to help him get past the elephant. We went along to see what happened. The elephant, apparently unhappy at the presence of a significant group of people, carried out a mock charge towards us. John had previously explained that, when you get very close to elephants, you can tell by their behavior and “ the look in their eyes” whether they're likely to be seriously dangerous or not. Well he proved his point, and his courage, but standing his ground, clapping his hands and shouting. You really needed to know it was a mock charge! For the inexperienced it looked serious enough to warrant a swift departure from the area, but the elephant wasn’t really serious – he pulled up a couple of metres from John, flapped his ears and waved his trunk and turned away.

A highlight of our stay at Eagle Island was a helicopter ride over the Delta; exhilarating as the doors were off the chopper and we sat on the edges of the back seats with our feet on the skids. The trip provided wonderful oversights of the ecological structure of islands and swamp, as well as views of animals from the air, including a herd of buffalo which we had not seen from the ground. We also saw hippos submerged in the channels that they make through the vegetation.

Aerial view of a large island, with buffalo

Overall it was a great way to spend a few days in a relatively unspoiled part of Africa. If you had to live anywhere in Africa, Botswana would be the place – although you can bet there would be unforeseen problems. For visitors, the travel to get there is slightly tedious and Johannesburg, which you have to go through, is not nowadays an attractive city. It's tense and dangerous and the residential areas look more like prison camps than suburbs, although residents would undoubtedly take exception to this description. However the new Gautrain, which runs from the airport into town is smooth and quiet and very efficient. The airport itself, greatly upgraded for the football world cup last year, is also modern and efficient. It’s just the government that seems to be running down.