The recent equinox marked a significant change from a very hot and rain-free couple of weeks to relatively cool conditions, and rain is forecast every day for the next ten days at least. This sudden change had me reflecting on the seasons and how they are represented in our neck of the woods.
Of course that the equinox marked such a change was entirely coincidental. This summer, the eastern side of South Africa (where I live in the province of KwaZulu-Natal) has had more than usual rains, although many regions in the country remain stuck in horrendous long-term drought conditions. Our fairly localised higher-than-normal summer rainfall is said to be because the El Niño-Southern Oscillation (ENSO) cycle is currently in the cooler La Niña phase, a phase that is forecast to diminish as the year progresses.
A summer storm rumbling in – picture taken in January this year. The small green tarp visible on the roof of our house covers a damaged skylight that was smashed in a severe hailstorm late last year. (Only this month repairs to the hail damage to the house were finally completed.)
In South Africa there is no officially designated schedule of the seasons and we tend to follow the three-months-per-season convention that is often based on the divisions of the solstices and the equinoxes. However, these divisions may not accurately correlate to weather patterns. Identifying the seasons is significant for many human activities and for resource management from agriculture to tourism.
A topographic map of southern Africa. The small landlocked mountainous country towards the eastern side that is outlined in red is Lesotho. I live in Pietermaritzburg, which is on the edge of the escarpment that rises up between the coast and the mountains that border the eastern side of Lesotho. (Map: Wikimedia Commons. Topographic map of South Africa. Created with GMT from public domain GLOBE data. 21 June 2007. Author: Sadalmelik.)
South Africa is considered to be a largely semi-arid country and it is situated in the subtropics (with a northern top corner peeking into the Tropic of Capricorn). The country is subject to a variety of weather systems and its regional weather patterns are also influenced by a variety of factors such as proximity to the long coastline as well as considerable variations in altitude including the presence of a large inland plateau.
September raindrops in our garden after the long dry months of winter
In South Africa some regions have the bulk of their rainfall in the colder months and others in the hotter months, but with significant inconsistencies across regions. In the arid and semi-arid regions the scarcity of the rainfall means that it cannot be used as an indicator of the seasons. In addition to distinct differences in rainfall across the country, the temperatures too can vary tremendously.
Early summer (November) flowers in a patch of the increasingly rare and threatened natural grassland areas in the KwaZulu-Natal Midlands
In a recent study (Van der Walt & Fitchett, 2020), daily temperature readings taken from records from 35 weather stations over a period of 35 years (1980 to 2015) were collated and the data was used as a statistical basis for classifying the seasons. Of course there were variations across regions and altitudes but on average summer was found to be the longest season (October to March) with winter occurring June to August. The greatest variability was in the onset and ending of spring and of autumn, but typically spring is in September and early autumn in April and late autumn in May.
The most significant regional differences are that summers start later and winters end later in the south western regions, and in the northeast summers start earlier and winters end earlier.
Spangled with raindrops an indigenous gerbera (Gerbera ambigua) when in full bloom in our garden in spring. These lovely daisies continue flowering well into summer
At the weather stations closest to Pietermaritzburg that were used in the study, it was recorded that spring-like temperatures may commence as early as August and late spring temperatures may continue through to November – so there is a rather gradual merging of spring into summer in this region.
A major significance of temperature is that air temperatures are directly related to ‘phenological shifts’ – i.e. temperature has a direct influence on periodic biological phenomena such as breeding, flowering and migration.
Butterflies are most prolific in our garden in the months of late summer and early autumn. I photographed this Natal acraea (Acraea natalica natalica) in our garden on a hot afternoon last week
I expect that almost everybody across the world is experiencing at least some of the effects of climate change, be they in the form of extreme weather events or noticeable increases in average temperatures. Shifts in climate trends that have already been observed in South Africa (1960–2010) include annual increases in maximum and minimum temperatures across the seasons and in most zones. Mean annual temperatures have increased by more than 1.5 times the observed global average of 0.65°C (SANBI factsheet).
A view photographed from a high ridge in the Fort Nottingham area of the Kwa-Zulu Natal (KZN). A patch of indigenous forest can be seen to the right of the photo in the lee of the high ridge, and the dark green patch of trees in the distance is a commercial plantation of exotic trees – probably eucalyptus
Some of the forecast climate change trends for southern Africa relate to increasing average temperatures especially inland (with predicted increases being as high as 5–8°C by 2050), with a corresponding decrease in rainfall especially across the western regions and the interior, whereas the eastern areas is likely to be wetter, including high intensity rainfall events.
Beef cattle being moved to paddock early on a misty morning in the summer on a farm in the KZN Midlands
By contrast, here is a view of KZN Midlands farmland in the dry winter months. This photo was taken in the month of June near Mooi River
The last flowers of the wild dagga (Leonotus leonurus) in early winter, seen together with grasses that have gone to seed as they grow on a strip of grassland between an indigenous forest patch and grassland used for grazing cattle. Some of the trees in the background are naturalised Black wattle (Acacia mearnsii) trees. Black wattle trees were first introduced to South Africa from Australia to be grown commercially to provide a bark extract that can be used for tanning hides. The wood is used for lumber, it is chipped for paper manufacture, and it makes good firewood but the naturalized trees have become highly invasive
On the other side of town and at a lower elevation, this is a view of the natural bushveld in the Lower Mpushini Valley where the flowers of Aloe Ferox (also known as Aloe candelabrum) are a prominent feature in winter
Aloes are far from being the only winter flowering indigenous plants. Although in some respects red-hot poker (Kniphofia) flowers may remind one of aloes, unlike aloes Kniphofias are not succulents. Some species of Kniphofias flower in the summer and others are winter flowering, such as the Kniphofia praecox pictured above flowering in our garden in June
Butterflies feeding on winter flowers of a Crassula species in winter in June at Cumberland Nature Reserve, which is not far from the eastern side of Pietermaritzburg
Small and cheerful gazanias (probably Gazania krebsiana) in flower in a burnt area of grassland at Kamberg Nature Reserve in the Drakensberg region in KZN
Shifting focus from flowers to leaves, although many indigenous trees are deciduous we do not have the spectacularly colourful falls of leaves in autumn as in so many northern hemisphere regions. Many of our deciduous trees drop their leaves suddenly in winter, and in wetter areas with milder winters they may tend more to being semi-deciduous even retaining some of the old leaves as the new leaves are appearing in the spring.
For example this white stinkwood (Celtis africana), on the margins of our garden, retains its leaves in April in early autumn. The bird is an olive thrush (Turdus olivaceus)
In our area where the winters are mild, by July the leaves of the white stinkwood are changing colour with some leaves already having fallen
By July the white stinkwoods in our neighbourhood are completely bare of leaves
The fallen leaves carpet the ground in a lovely layer of mulch. Thrushes and other birds have a fruitful time tossing aside the leaves searching for food
During September the white stinkwood trees become flush with beautiful new leaves. The tree’s small flowers and tiny fruits appear during the summer
We do have one indigenous tree in the garden that has spectacularly colourful leaves although not all the leaves change colour at the same time so the effect is not as dramatic as it might be. This is the forest bushwillow (Combretum krausii), which in milder areas may only be semi-deciduous
And to end off this post, I have rather randomly selected a photo from each season.
Another photo of Gerbera ambigua flowers in the mini grassland in our garden in the spring
A clearing in mistbelt forest in the KZN midlands where the forest spurflower (Plectranthus fruticosus) was flowering in the late summer
A common waxbill looking for seeds in the golden bristle grass (Setaria sphacelata sericea) in our garden during the early autumn month of April
An increasingly rare sight in our garden is winter frost. Although we still may get frost on a few winter nights in the more exposed parts of the garden, we never do get as much frost as in the nearby valley below us. The last widespread frost we experienced was in the winter of 2014 when even water in the birdbath froze. The delicate powdering of frost pictured above occurred in the same year
And to end, here is another photo of the glorious sunrise photographed in January 2018 in the KZN Midlands. This photograph was taken seven minutes earlier than the header photograph at the top of this post
SANBI. [n.d.] Climate trends and scenarios. Climate and Impacts Factsheet Series, Factsheet 2 of 7. https://www.google.com/search?hl=en&q=climate%20change%20south%20africa%20forecasts
Van der Walt, Adriaan J. & Jennifer M. Fitchett. 2020. Statistical classification of South African seasonal divisions on the basis of daily temperature data. South African Journal of Science. 116(9/10). 15 pages. https://doi.org/10.17159/sajs.2020/7614
Posted by Carol