Cape Town, in South Africa, is famous for its dramatic mountains and coastline, but its greatest treasure lies in the plants that carpet its slopes and valleys. Table Mountain National Park and its surrounds are home to 2,785 species, including subspecies and varieties.
This is more plant species than in some European countries and national parks in the United States.
We are a group of botanists and conservation scientists who set out to update the plant species checklist for the Cape Peninsula. This checklist was first published 76 years ago in 1950 and our checklist is the fourth major update.
For the latest update, we collated data from diverse sources, including herbaria, conservation agency databases and iNaturalist, an online social network where people can upload photos of the natural world. These new technologies allow us to rapidly gather new data for checklists that assist conservation managers to prioritise and respond to threats.
Our new, updated checklist provides insights into the city’s flora, from showcasing the global significance of its endemic plants to the unique ecology that has shaped this diversity.
Here are six important insights highlighted by the list:
1. A global biodiversity hotspot and world heritage site in one city
The number of plants species per-unit-area on the Cape Peninsula is among the highest in the world. This makes Cape Town a true biodiversity capital. It also makes Table Mountain National Park one of the most botanically diverse protected areas in the world, especially for species found nowhere else on the planet. The park forms part of the Cape Floral Region Protected Areas Unesco World Heritage Site.
2. Unusual plant families and unique species characterise the Fynbos landscape
Fynbos is a unique type of vegetation that only grows on the southern tip of Africa. The Cape Peninsula is dominated by a unique combination of families, including reed-like restios (Restionaceae), showy proteas (Proteaceae), delicate heath-like ericas (Ericacaeae), colourful irises (Iridaceae), and unusual pea groups (Fabaceae).
Other families, like the blacktips (Bruniaceae), are found nowhere else in the world except in the Cape Floristic Region, which Cape Town is part of.
Within this floral tapestry lie at least 158 species that are found nowhere else on Earth.
3. Treasures are threatened
The richness and rarity of the plants comes with great risk: hundreds of species are threatened with extinction. In fact, Cape Town is the extinction capital of the world for flowering plants, based on the number of plants that have already gone extinct.
Our checklist identified 261 threatened species, including 38 that are Critically Endangered. These endangered species include irises, ericas, orchids, proteas and daisies.
Read more: Lost fynbos seeds from underground ‘time capsules’ in South Africa can grow again – new study
Many species cling to tiny fragments of remaining habitat, making them especially vulnerable to disturbances.
Threats to these species include habitat loss, alien species, fire suppression and trampling. Many species have not been seen for decades on Table Mountain. This includes some erica and orchid species, such as Disa physodes.
One reason for this is that natural fires are put out to prevent them from spreading. Yet fynbos depends on fire for regeneration, and many species flower spectacularly after burns. Therefore, all fynbos areas need natural or prescribed burns every 10-20 years to maintain fynbos ecology.
Read more: The Table Mountain fire: what we can learn from the main drivers of wildfires
Because some invasive plants have also adapted to fire and flourish after a burn, teams of people are needed to keep removing new invasive plants that grow after planned and wild fires.
4. The alien invasion problem
At least 437 non-native species occur wild on the peninsula. Wattles (Acacia), gum trees (Eucalyptus), clovers (Trifolium), pines (Pinus) and invasive grasses (Poaceae) are among the most problematic.
They compete with indigenous plants for space, make fires fiercer and more frequent, use up precious water and also choke freshwater systems. However, national parks staff, Working for Water clearing teams and volunteers have cleared over 3,300 hectares of invasive plants. This has allowed natural vegetation and processes to flourish – even resulting in some species reappearing after decades of not being seen.
5. Small, specially adapted plants rule the peninsula
There are 1,078 non-woody plant species growing on the Cape Peninsula, making them the most dominant growth form. Together with 607 types of dwarf shrubs (plants that are under a metre tall) and 590 species of shrubs, these make up 70% of the flora on the mountain.
Trees make up only 2.5% of the plant species on the Cape Peninsula. Forest covers 5% of the peninsula, and all forests there are protected. But protected areas only cover 30% of the land where Critically Endangered Peninsula Granite Fynbos occurs, 10% of the land supporting the Critically Endangered Peninsula Shale Renosterveld, and less than 1% of the land supporting Critically Endangered Cape Flats Sand Fynbos.
Read more: Removing alien plants can save water: we measured how much
Interesting shrubs and bulbs grow in these vegetation types. They have extraordinary adaptations to dry summers, poor soils and fire, surviving these harsh conditions through seasonal life cycles and underground storage.
6. Science never stands still
New discoveries and revisions keep reshaping the checklist. New techniques, such as DNA analysis, allow for better understanding of the relationship among different species. There are continuous discoveries of new species – a total of 18 species that were new to science have been described from the Cape Town area since 2000. One of these discoveries was the hidden veldrush (Schoenus inconspicuus), a small, inconspicuous sedge, with paperlike spikelets. Only four of these plants have been found.
Meanwhile, plants continue to go extinct, such as the green-and-red isolepis (Isolepis bulbifera), which lost its wetlands.
Science-based projects to cultivate endangered plants in nurseries and then plant them on the peninsula have led to some species being successfully reintroduced. They include the Extinct in the Wild whorled heath (Erica verticillata), which was discovered in cultivation in European botanical gardens and has been reintroduced into four suitable nature reserves.
Why this checklist matters
The updated checklist is not just a list of names providing statistics on the flora of the Cape Peninsula. It is a tool for action. It guides restoration projects, climate change vulnerability assessments, the management of fire and alien clearing, and how activities, like construction and roads, are zoned in a way that helps Cape Town’s unique natural heritage survive for future generations.
Read more: Africa’s plants: a database project has recorded 65,000 species – and is still growing
Cape Town’s flora is also important because it shapes water security for the area and provides a buffer against climate change. Fynbos is adapted to drought. More water is available in landscapes dominated by indigenous fynbos rather than thirsty alien trees that use more water. The flora is also a key draw card for tourists and a global heritage asset.
The new checklist is a reminder that biodiversity is both fragile and dynamic. By understanding the uniqueness of its flora, we can see the city in a new light. It is not only a place of scenic beauty, but a global hotspot of plant diversity whose future depends on careful monitoring, management and safekeeping.
Dian Spear previously worked for South African National Parks, and she received funding from the JRS Biodiversity Foundation for this work.
Nicola van Wilgen-Bredenkamp works for SANParks and received funding from the Table Mountain Fund for this work.
Patricia Holmes has a SANParks contract to help compile species' distribution and traits database.
Ronell R Klopper works for the South African National Biodiversity Institute (SANBI).
Tony Rebelo does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.
This article was originally published on The Conversation. Read the original article.
