Cape Town - The jury is still out on whether this Cape Town winter is particularly severe, but sun-worshippers take heart: researchers have found that the Table Mountain National Park is now much warmer than it was half a century ago.
However, that warming trend is probably bad news for many of the park’s unique fynbos plants and other endemic species, which may be struggling to adapt.
Although actual minimum and maximum temperatures have remained relatively constant – apart from April and May, which have both experienced significant increases in the maximum recorded – there’s been a significant increase in the average annual minimum and maximum temperatures, so that it’s now on average 1.25° C warmer than in the middle of the 20th century.
The researchers also found that rainfall events in the Table Mountain National Park are getting slightly bigger than they were during the first half of the 20th century and are happening within a shorter season, while weather stations in some other national parks to the east have recorded huge rainfall reductions.
There are six national parks that conserve unique fynbos vegetation to some degree – Table Mountain, West Coast, Agulhas, Bontebok, Garden Route and Addo – and the reseachers have detected significant increases in both monthly, and in annual minimum and maximum, temperatures in four of these parks, including Table Mountain.
Overall, the fynbos national parks – especially those towards the east of the fynbos region that extends into the Eastern Cape – appear to be getting drier, rather than wetter, contrary to climate change predictions.
However, none of the data revealing these changes has yet been subjected to close analysis, warns scientist Nicola van Wilgen of SA National Parks’ Cape Research Centre at Tokai. She is one of four core members of SANParks’ climate change team, and she revealed some of their research at the recent Fynbos Forum conference in Cape St Francis.
Van Wilgen explains that their work is part of a global environmental change project that is loosely following the global Millennium Ecosystem Assessment conducted in 2005.
It involves examining six drivers of change: invasive alien species, climate change, disease, habitat change, pollution and river health, and the over-harvesting of natural resources, and SANParks has a team of researchers working on each of the six. She is managing the project and working in the climate change, alien species and natural resource harvesting teams.
The climate change team is assessing current trends in climate change in, and the possible impact on, all 19 national parks, although Van Wilgen only reported on the “fynbos” parks’ data because of the nature of the conference.
Data from the Cape Point station is particularly useful because there are temperature records going back 50 years and rainfall figures for 110.
Temperature changes in the Table Mountain National Park have been dramatic, based on this station’s readings. The average maximum and average minimum temperatures have both increased in every month of the year by between 0.01° and 0.03° C per year, or about 0.3° C per decade.
The 1960 mean annual maximum temperature of 18.4° C has increased to 19.6. “So over 50 years that’s 1.2° C – that’s quite a lot!” Van Wilgen says.
The only significant annual rainfall trend that the team has found in the Table Mountain park is an increase in the number of heavier rainfall events, compared to the first half of the previous century. However, this increase is only 0.7mm per event – “Not huge,” she says. The team has also found that the annual season during which most of the rain falls has shortened by a few days, but the overall rainfall has remained constant.
Much bigger rainfall changes were detected in other parks, with the most significant at Addo where one station recorded an average decrease of 272mm over the last 90 years. Less dramatic decreases in total rainfall were also detected in the Bontebok (Swellendam) and Garden Route parks, although the Bloukrans station in the Garden Route park recorded an average decrease of 158mm over 110 years.
Van Wilgen explains that the climate change team is still in the process of writing up the data.
Why are they doing the work?
“Obviously these kind of changes are going to have biodiversity implications, and there’s evidence from other parts of the world that such changes are already being realised,” she responds. For example, earlier flowering seasons are an obvious concern, because insect pollinators may not have been able to make the necessary life cycle adaptations in time.
While national parks are static entities and can’t physically avoid climate change, knowing what’s likely to happen does allow managers to plan to mitigate the likely impacts.
“Managers are also more likely to allocate time and funding to things that they understand well, so if you can show them the evidence – ‘Look, this is what’s happening in your park’ – then the more likely they’ll be to make informed decisions in the future. That’s been documented internationally,” Van Wilgen says.
Cape Argus