It's well known and documented that Cape Town is one of the world's "hottest of hotspots" of plant diversity, with many species that occur naturally nowhere else on Earth.
But the city is facing a "biodiversity mega-disaster" in its efforts to conserve this treasure chest of nature, warns Dr Tony Rebelo, a senior scientist at the SA National Biodiversity Institute at Kirstenbosch and one of the country's top ecological researchers.
In fact he goes further, referring to the city's current conservation crisis as "a mega-disaster of all mega-disasters".
At face value, the city seems to be doing quite well in conservation terms, with 21 percent of the municipal area under some form of conservation management - substantially higher than the international benchmark of 10 percent advocated by the World Conservation Union (IUCN).
But Rebelo points out that this figure flatters only to deceive.
His institute's 2004 National Spatial Biodiversity Assessment categorises 400-odd vegetation types in southern Africa. Of these, 24 are rated as "critically endangered". Nearly all of them occur within the fynbos region of (essentially) the Western Cape - and nine of these vegetation types - or 34 percent - occur within the boundaries of the city of Cape Town.
And the latest evaluation, done in terms of the National Environmental Management Act and completed this year for submission to the Minister of Environmental Affairs, is even more dire. This rates 21 vegetation types as "critically endangered", of which 11 - just over 50 percent - occur in Cape Town.
There's more bad news: a further three of the 12 national vegetation types that are only marginally less at risk, with an"endangered" rating, are also found within the city's boundaries.
And just to complete the seriously gloomy picture, one-third of all the critically endangered terrestrial vegetation types - a tiny handful are wetland systems - are endemic to Cape Town, growing naturally nowhere else in the world.
It's immediately apparent why this is so: habitat transformation, explains Rebelo. Agriculture (66 percent) and urbanisation (33 percent) are today the major permanent transformers of the natural habitat.
The first vegetation type to be transformed by European colonisers arriving in the 17th century was Peninsula Shale Renosterveld, of which just 11 percent of the historical extent remains. Only 10 percent of this remainder is conserved, while the national conservation target for this vegetation type is 26 percent - "a pipe-dream", says Rebelo.
Cape Flats Sand Fynbosape - and nine of these vegetation types - or 34 percent was the largest veld type in the metro area, covering about one-third of the entire lowland area. Now there is hardly any left, with the biggest patch anywhere south of Blouberg occurring in the middle of Kenilworth race course.
Another major problem is fire - or rather, the lack of it, he notes.
Even small areas of remaining natural fynbos must burn to survive, but getting permission, and on the right kind of day for natural fires - hot and windy conditions - is extremely difficult.
"This lack of permission to burn means that on the Cape Peninsula, only about one-third of the area required to be burnt to maintain the optimal 15-year fire cycle, actually burns. Ironically, arsonists are the saviours of fynbos," he says.
The City of Cape Town municipal area hosts more than 2 500 plant species and has the highest density and number of threatened plants of any metropolitan area in the world, Rebelo adds.
"This number has increased dramatically in the last decade, according to the latest Red Data List from April last year. But I don't believe these official figures, though - they are a serious under-estimate.
"We know there are 2 200 species just on the Peninsula alone. I suspect that the figure for Cape Town is well over 3 000 plant species, and perhaps even 3 500 - this is more than twice the number in the whole of Britain!"
The city has already lost seven plant species that have become totally extinct, with another three being extinct in the wild. But according to the latest figures from 2008, 319 individual plant species are listed as Critically Endangered, Endangered or Vulnerable, while the number of extinct plants is given as 13. Only six countries worldwide are currently known to have more threatened species than those listed.
How did we get into this mess?
"Well, it sort of sprung up on us," answers Rebelo.
From 1652 until 1800 Cape Town was "a sleepy little town nestled in the amphitheatre of Table Mountain". Even at the start of the 20th century there was little expansion, but after World War 2 "all hell broke loose".
By 1977 the city had doubled in size; by 2002 it had doubled again; and by 2020 it will have doubled for a third time. "Today it's a monster consuming 12km² of new land every year."
There have been some positive milestones, such as the hand-over of state forests to conservation in the 1980s and the declaration of the Table Mountain National Park in 1998, says Rebelo.
But, excluding the World Heritage Site status of the Peninsula and new contractual land being added to the national park and at Koeberg, nothing significant has been done since 1960 to acquire new conservation land within the city's borders. Despite repeated studies for achieving conservation goals by the city, there has been no action on the ground, he argues.
Rebelo's solution? The 37 "Core Areas" identified as vital for conservation by the Botanical Society and three areas managed as nature reserves by the city but without formal conservation status - Macassar, Mamre and Kogelberg - must all be given the highest conservation status as soon as possible.
"This is what we require and we require it now. This is the land that must be secured immediately for conservation if Cape Town is to come even close to trying to meet its national and international obligations to protect the Cape Flora, which occurs nowhere else on Earth. This is the bottom line."
Cape Town has just 10 years left before the city expands and covers everything, Rebelo stresses.
"And we have to double the size of the conservation network, from 21 percent to 37 percent before that happens.
"We have a biodiversity mega-disaster in Cape Town, perhaps the biggest on the planet. And the situation in the lowlands is perilous!
"This is a huge challenge. To turn this crisis around will require budget and resources and the support of the politicians."
While the city is preparing plans to tackle this disaster, private, national and international help will probably also be required, Rebelo adds.
"For 10 plant species and eight vegetation types it is already too late. But unless we move into top gear immediately, it will also be too late for another 300 plant species and 12 vegetation types. So above all, we need urgent action now!"