BuaNews (Tshwane)
Emily Visser
27 February 2008
Johannesburg — Climate change is being brought home to ordinary Johannesburg residents, who have noticed trees shedding their leaves early and plants flowering out of season, or not flowering at all.
In response, planting trees is a small step each resident can take, according to the Johannesburg official website.
Alan Buff, the general manager for technical support and horticultural training of Johannesburg City Parks, says that over the past five years the effects of climate change have started to become more pronounced in the natural environment.
Mr Buff points out that global warming is a natural event - some scientists believe climate change is much more likely to be part of a cycle of warming and cooling that has happened regularly every 1 500 years for the last million years.
"It would have happened anyway, but we are accelerating the process."
It is only the end of February and the leaves are already changing colour. Earlier in the month the morning air surprised everyone with its crisp autumn pinch. Around the country people have reported the early blooming of certain species of plants.
Cosmos, an early autumn bloomer, started flowering as early as December. Some people reported mass displays of the annual. Clivias and azaleas, both early spring bloomers, were also found blooming in certain gardens this month.
These are just some of the changes in nature that have concerned people. We have come to know it as climate change - and its long term effect bodes ill for mankind.
Normal carbon dioxide levels in the air are 300 parts per million; this figure has increased to 370 parts per million. The balance in the stratosphere, our life-giving barrier, has been disturbed, leading to ozone depletion.
"The chemical soup has been thickened," Mr Buff explains.
He says a noticeable effect of seasonal change on the Highveld is the higher light intensity we are experiencing, causing stress to trees. "Leaf drop is earlier and can be throughout the season."
Another effect is an increase in humidity, leading to more fungal infections. Rain patterns have also changed, with higher water volumes experienced at any given time.
Because of excessive urban development, this water runs away instead of seeping into the ground to feed the groundwater system, which in turn replenishes our rivers.
"Plants grow quicker but are weaker because they are not taking in enough nutrients," he explained.
This leads to a knock-on effect on insects and bird species, which rely on the exact seasonal flowering or fruiting of plants to survive. Farmers are especially at risk, with crops needing a specific seasonal period and circumstances in which to grow.
"Johannesburg lies high above sea level. What we have been noticing is lots of plants are becoming stressed."
City Parks started looking into seasonal change on a more intensive scale about two years ago. It aims to plant 200 000 trees over the next two years.
"We are trying to correct the [environmental] balance with tree planting," said Mr Bluff.
It follows a strict regimen in which 80 percent of trees planted must be indigenous. But indigenous trees have very specific needs and are often unsuited for high density city streets.
For one, indigenous trees do not like to be pruned and trimmed excessively, a given for street trees as they have to be shaped to make way for telephone lines, large vehicles and pedestrians.
Indigenous trees also do not deal as well with pollution as the hardier exotics. That is why City Parks often opts for birches, oaks and plane trees for high density streets. Good local varieties are Celtis Africana (white stinkwoods), Rhus lancea (karee) and the various hardy acacias (thorn trees).
Mr Buff often has to answer queries relating to tree planting and the effect of this on the country's water shortage.
Planting more trees is definitely the answer, he confirms. Almost all the new trees the City is planting are watered with grey water, and just a small percentage is watered with fresh water. Grey water is obtained from the final purification stage of the City's sewage works.
By utilising grey water, which otherwise would have been put back into the river systems, the new trees are, in effect, contributing to purifying the water system in an indirect way.
"People don't realise the value of trees - they are an asset for humanity," said Mr Buff, as each new tree planted by City Parks costs R1 000.
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Over 400 World Wide Prominent Scientists Disputed Man-Made Global Warming Claims in 2007. See http://tinyurl.com/2dv6nz