Veld & Flora Feature



​Win-win with the What-The-Hack workout


Whether you are keen to join the global trend to be more mindful about your outdoor leisure or looking for a sport or outdoor adventure activity that gives back to the environment, hacking invasive alien trees could be just what your body and mind need


JAN 12, 2022 | By Donovan Kotze & Alanna Rebelo. Photographs: Donovan Kotze

Win-win with the
What-The-Hack workout


Above: “Hacking is great for fitness and fun,” says recent recruit Roderick Juba, “and it’s wonderful to know you’re helping care for our environment.”


Is your new year resolution to exercise more? Since ancient times, exercise has been one of the cornerstones of good health – but even now, all our public-health experts, sports scientists and biokineticists have not cracked the secret of what makes one person stick to an exercise programme and another fall by the wayside.

What they do know – and many of us can identify with – is that exercise should not just be a repetitious slog. If you enjoy the exercise you do, you are much more likely to return to it if holidays, illness or injury see you fall off the wagon.

As a BotSoc member, you enjoy South Africa’s indigenous plants and are interested in getting to know and protect them. And there is an exercise hack for that – hacking, or what you could call the What-The-Hack Workout.


Above: Hacking helps prevent invasive species such as hakea and maritime pine taking over beautiful ecosystems.

What the hack? 

Hacking is about helping to make space for our indigenous plants by cutting down invasive alien trees and bushes, usually with a handsaw or loppers and tree poppers, or sometimes also pulling out seedlings by hand. There is huge scope for hackers from eight to 80 years old – you just need to match yourself to the difficulty, challenge and pace at which to hack.

Beginner hacks would usually be on gentle slopes, where you would not have to walk far. This is also where hand pulling is most frequently needed.

Advanced hacks would be in hard-to-reach places – think mountain ridges or slopes – and would usually involve sawing. Whatever your ability, there is something for you.

Roderick Juba, from Mossel Bay in the Western Cape, works for the Water Resource Commission and recently started hacking. “My hacks in the Klein Karoo have been a lot of fun, great for fitness,” he says. “It is brilliant to know that you are assisting with maintaining critical ecosystem services.”


What-the-hack payoff

Hacking invasive alien trees has all the thrills, challenges and satisfaction of other outdoor sports, even satisfying a hunting instinct for some hackers. The exhilaration of bringing an alien hakea tree crashing to the ground compares with the exhilaration of mountaineering or mountain biking, with a bit of the satisfaction of landing a fish thrown in.

Hacking offers a serious all-over cardiovascular workout that compares well with mountaineering or canoeing. Reaching the trees works your lower body and cutting them down works your upper body.

You may sometimes need to scramble over difficult terrain and through thick bush – but ask mountaineers, trail runners or mountain bikers and they will tell you that triumphing over difficult conditions adds to the glow of achievement.


Above: All geared up – hackers from the Mountain Club of South Africa, Worcester section.


A growing sport

Exercise, exhilaration and contribution to conservation all combine to make hacking a growing sport across South Africa. Hacking is most prominent in the fynbos region, where groups such as the Mountain Club of South Africa Cape Town section and the Kleinmond Hack Group have been hacking for more than 40 years. Some of the more active groups, like Friends of Tokai Park, have scores of volunteers and run three hacks a month.

Hackers are needed right across the country in all South Africa’s different natural habitats (biomes). As the interest in hacking starts to grow, so too has the number of hacking groups.

In Mpumalanga, for instance, invasive alien plants such as pine and black wattle are among the greatest threats to some of the last remaining areas of unique quartzite grasslands and indigenous forest around Kaapsehoop. Thankfully, Friends of Kaapsehoop’s enthusiastic volunteer group carries out at least one hack every month, pushing back the invasive alien plants from this critical habitat – and having plenty of fun at the same time.

In the savanna biome’s more humid areas, volunteer hackers can help control many key invasive alien species such as chromoeana, lantana and bugweed. It is especially important to remove young plants that are yet to flower – these can often be hand pulled.

In the highveld grasslands, particularly around Johannesburg, there are also problems with lantana and bugweed. Friends of the Melville Koppies have perfected the technique of effectively removing bugweed with no herbicide by cutting it below ground.

Across all the biomes, volunteer hackers can play a critical role in catching garden-escapee invasive alien plants such as cannas before they infest the natural vegetation or urban open spaces.


The art of
safe hacking

Safe hacking is always paramount, so make sure that:

  1. You have the right equipment for the job, up to and including protective gloves.
  2. You hack only in areas where you can safely access the trees. Luckily, the main invasive alien trees of the mountain fynbos areas – hakea from Australia and maritime pine from the mediterranean region – do not require chemicals to prevent the regrowth of cut trees.
  3. You cut the hakea or pine down below the lowest branch with live leaves to prevent it resprouting. Some alien trees, such as gums and acacias, need chemical treatment to stop them coppicing. Be sure what
    you are dealing with and your
    efforts will not be wasted.



Once you have decided that hacking is a sport for you, add an extra layer of fun with a hacking challenge. Here are two examples:

  • The 10 000 Tree Mountain Fynbos Challenge:

    This project marks every 10 000 alien trees hacked from fynbos and celebrated its third 10 000 hacked last year.

    So for every hack you undertake, please upload a few photos and locations to

  • Adopt-a-Plot: Recently launched by Friends of Tokai Park, you adopt a plot of ground in Tokai Park (part of Table Mountain National Park) for a year or longer, clear it of aliens and make sure it stays cleared: The Friends provide all necessary training:

Adding value

Your work in helping to control invasive alien trees cares for our environment in three ways. Left alone, these trees intensify wildfires. They also reduce precious water supplies. In addition, they also threaten South Africa’s globally significant biodiversity areas, particularly mountain fynbos where invasive alien trees, such as hakea and maritime pine, continue to spread.

Invasive alien trees can make fires significantly more severe. This was seen to our grief and horror in the disastrous 2017 Knysna fires, where seven people died and more than 400 homes were destroyed. More recently, Cape Town’s Table Mountain fire was also devastating for our cultural heritage, destroying Mostert’s Mill and critical archives in UCT’s Jagger Library.

Even when not burning, invasive alien trees cause a different ecological disaster because they are much thirstier than indigenous vegetation. If invasive alien trees are not controlled, they guzzle many millions of litres of water annually. This reduces water for plants, veld creatures and humans.

During droughts particularly, this can also affect the households and businesses that depend on this water. If left unchecked, invasive alien trees can spread densely over mountain areas to become an inhospitable sea for the remaining indigenous fauna and flora.

“Research shows that we are, in fact, going backwards,” says Dr Tony Rebelo from the South African National Biodiversity Institute. “Aliens are reinvading despite efforts to control them.”

The considerable efforts by government to clear invasive alien trees, such as through the Working for Water programme, have not been sufficient. That turns taking up the What-The-Hack Workout from a fun challenge into a valuable contribution to protecting and conserving our environment.


Above: Long-standing hacker Donovan Kotze says: “Hacking remains my number 1 sport – even after many years, the enjoyment that I receive from a challenging hack never wears off!”


Where can I sign up?

If you are new to tree hacking, start with an established hacking group. Many of these groups have a monthly or sometimes weekly hack to which newcomers are always welcome. In the Cape, for instance, there are currently at least 20 different active groups. If you would like to find a group or event near you, scan this QR code:

Right: Triumphant hacker Samantha Adey.


Dr Donovan Kotze is an honorary research fellow with the Centre for Water Resources Research, University of KwaZulu-Natal and hacks with the Mountain Club of South Africa, South Cape section.

Dr Alanna Rebelo is a postdoctoral research fellow in the Conservation Ecology and Entomology Department at Stellenbosch University and when in the southern suburbs hacks with the Friends of Tokai Park. 

This article was first featured in Veld & Flora in the June 2021 edition. Veld & Flora is a special benefit for Botanical Society members.

To read this article and others like it in Veld & Flora become a BotSoc member today:


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