Hortgro Industry leadership programme | Dr Tara Southey 

A graduate of the first Hortgro industry leadership programme talks about climate change and modelling and shares her reflections on the programme. By Anna Mouton.

Hortgro launched its industry leadership programme in 2022 to expose the next generation of industry leaders to industry structures and programmes. Researcher Dr Tara Southey was one of the first graduates.

Southey grew up on a sheep farm in Victoria West and remains in love with the Karoo. She studied Viticulture and Oenology at Stellenbosch University. Her fascination with the interaction between a crop and its environment led to her MSc in Viticulture, which examined the effect of soil, irrigation, and climate on wine quality.

She went on to complete her PhD on the impact of climate change on the wine industry. This led to her proficiency in GIS, remote sensing, open-source tools, and climate analysis, eventually culminating in the development of TerraClim, a climate database that provides growers with detailed field-level climate and terrain data.

Q. How is climate change likely to affect Western Cape agriculture?

Everybody’s climate vulnerability is expressed differently, so not everybody’s adaptation or mitigation strategy looks the same. If we don’t understand that in the agricultural context, we’ll have problems.

For example, an area like Robertson has been cooling in the minimum profile, so it is getting more frost. Certain farms that have never experienced frost are losing up to 30% of their harvest due to random frost events in September or October. But the region produces incredible wines!

Other scenarios we’re seeing involve many people perceiving heatwaves this past season, but according to the data, we never received a heatwave—a heatwave is 5 °C warmer than the average maximum monthly temperature for three consecutive days.

This season, we saw more hours above 35 °C, attributed to less sea breeze than normal. So, this past summer, we had higher night temperatures, which link back to a crop’s physiological recovery and effect, for example, the colouring of blush apples and pears.

For me, the impact of climate change is increased seasonal variability, the change in maximum-minimum profiles, and the number of hours within those profiles. We can’t just continue to look at maximum and minimum daily temperatures. Understanding climate profiling is important in the context of climate change.

Now, we plant cultivars that the market wants — we’re not planting for future resilience in agriculture. What’s important for me is the impact of climate on food security. How do people adapt in an area like the Klein Karoo? What must they plant? We need a data-driven approach to help them.

Q. What are the data-related challenges facing South African agricultural climate modellers?

During my PhD I did internships in Italy and France. Their remote-sensing applications are much more robust than ours. Our results are not nearly as good as the Italian entity’s — we over- and underestimate temperature.

The reason is that the remote-sensing satellites are American. NASA positioned them specifically for their research. The satellites reach our orbit at less favourable angles and times, and the image is slightly warped, requiring orthorectification [processing to remove distortions].

It was during my PhD and postdoc that I realised that many resources that are deemed available are overestimating or underestimating readings. That’s when I started the drive for more weather stations.

Many people are still using open-source data when we should be considering more local solutions to understand each region’s vulnerability. The message I want to get across is that we can’t rely on virtual weather stations based on insufficient data.

Another problem is the inaccessibility of water data — the irrigation rights and current water use within catchment areas. You also need to know what crops were planted over the past three years.

It’s pretty much impossible to plant without supplementary irrigation under climate change. But there’s no centralised knowledge base for water data. I can climatically recommend what to plant based on the temperature profile, but if you don’t have water, you’re putting a noose around your neck before you’ve started.

Q. How can climate database technology and growers collaborate to improve climate models?

I’d like farmers to put up weather stations. Climate database technology can then correlate remote sensing with actual point weather-station data to do interpolations with digital elevation models so we can accurately model temperature.

This technology creates multiple virtual weather stations. We just modelled the whole of South Africa at a 1-kilometre resolution — there’s a new layer every hour. No satellite can provide hourly data.

We can help growers strategically place weather stations. I’d like the growers to put their data in a database that anybody can access. I’m trying to push to get data centralised and open so anybody can do something with it. That’s the only way we’ll advance climate mitigation and adaptation.

The other thing I probably say to every agricultural sector is that they must start collecting data on orchard level or per bin. I want them to become more aware of what data they’re collecting, what data are available, and how it can be integrated to find more intelligent solutions.

The goal is to plant the right crop and cultivar in the right place, which will give you the legs to have not only market traction but also climatic robustness.

One positive thing is that South African producers do not experience climate change like the rest of the globe. We’re not getting as hot as Europe. We are very buffered because the oceans regulate our environmental parameters.

We must learn to work with what we have, and our industry bodies must take a much stronger stance on our approach to climate change.

Q. What are your thoughts on the Hortgro leadership programme?

Sitting among other potential leaders and solving problems was so refreshing and impactful. All of us in the leadership programme were young and trying to develop innovative solutions. Still, I left there wondering what comes next — when will we turn those discussions into something tangible that we, as young leaders, have an opportunity to work toward?

It’s great to participate in a leadership programme and learn about the horticultural industry, but how will we impact the industry? The leadership programme was all about us learning, but now we need to go into another leadership phase — I think each group should implement something that will transform the industry.