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Kew's Millennium Seed Bank discovers why new saltbush seedlings along the Namibian coastline are struggling to survive

Kew’s Millennium Seed Bank rescues vulnerable vegetation along the Namibian coast to save the region’s plants and rare wildlife for future generations.

Isabelle Brunner sowing saltbush (Salsola nollothensis) seed into sheltered sites created using seaweed washed up on the shore (Photo: A. Burke)

Located in southwestern Namibia, the Sperrgebiet is a pristine wilderness rich in diamonds.

In this wilderness of high biological value, exploration for valuable alluvial diamonds in the early 1980’s led to the bulldozing of 40 metre wide trenches along some of the Sperrgebiet’s coastline. As well as in appearance, at 300 metres in length these diamond mining trenches have affected wildlife beach habitats, and in particular the salt-tolerant and woody shrub saltbush (Salsola nollothensis). To date very little natural recovery has taken place.

Determining the germination requirements of our seed collections at the Millennium Seed Bank is vital to successfully reintroduce plants back into the wild.

Rosemary Newton, Seed Longevity specialist at Kew's Millennium Seed Bank

Saltbush (Salsola nollothensis) is the dominant species in the Sperrgebiet region directly affected by diamond mining. With mounds towering up to four metres high, saltbush hummocks are crucial to the natural environment in this region. They stabilise sand dunes and support a range of plants and wildlife across 600km of Namibian coast.

Plant species that rely on healthy levels of saltbush hummocks to survive include the woody succulent species Galenia pruinosa, Drosanthemum luderitzii and Tetragonia reduplicata and the bristly lovegrass (Cladoraphis cyperoides). They also provide a habitat for rare and endangered animals like the desert rain frog (Breviceps macrops) and the Namaqua dwarf adder (Bitis schneideri). These unique and vulnerable animals are now even more at risk.

Sandy beach habitat with Salsola nollothensis hummocks in the distance

Photo: H. Kolberg

Kew's Millennium Seed Bank team investigates

Because levels of saltbush hummocks are crucial to the broader natural environment in the coastal Sperrgebiet region, Salsola nollothensis has become a cause for concern at Kew's Millennium Seed Bank partnership.

Working in partnership with the National Botanical Research Institute (NBRI) and Namdeb, a diamond mining company operating in the Sperrgebiet, plant scientists and conservationists based at Kew's Millennium Seed Bank at Wakehurst Place have started a programme of research to find out why the saltbush has failed to re-establish itself naturally in recent years.

Examination of seed collections by Kew’s team revealed that healthy seeds are largely absent from specimens from the affected Sperrgebiet region. This discovery has lead Kew’s science and conservation team to take a more active role to help this species recover in disturbed areas. Without healthy levels of seed, saltbush (Salsola nollothensis) is unable to reproduce effectively.

Since making this discovery, Kew’s science and conservation team have run a series of controlled germination tests on healthy seeds saved in Kew's Millennium Seed Bank to find out more.

Why Kew's MSBP is vital

Kew's Millennium Seed Bank partnership is vital for the future of coastal areas of the Sperrgebiet and the plants and wild life that live there.

This region is a beautiful and precious area of the Namibian coastline and the Millennium Seed Bank conservation team is working hard to ensure that it continues to support the diversity of life that has survived there for generations.

Restoring coastal vegetation in the Sperrgebiet region

Testing at Kew’s Millennium Seed Bank found that healthy Salsola nollothensis seeds germinated quickly at a range of constant temperatures. Scientists also found that seeds of the same health failed to survive when buried deep underground. Although seeds buried at depth did manage to germinate, they were unable to reach the surface of the soil to photosynthesize and so died prematurely.

To find out if seed burial is the cause of the decline in the growth of new saltbush seedlings in the Sperrgebiet region, the National Botanical Research Institute and Kew’s Millennium Seed Bank in partnership with Namdeb are leading a series of conservation trials to test out their theory.

The first of these tests aims to find out if protecting saltbush seeds from the unprecedented levels of shifting sand caused by wind channeling in diamond mining trenches could help this species re-establish. To do this Kew’s conservation team are forming piles of native seaweed around saltbush seeds to protect them from shifting sand and catalyse successful seedling growth. Raising seedlings in a nursery for transplantation will also be trialled.

Kew’s Millennium Seed Bank partnership is part of a global seed conservation network safeguarding endangered plant species for future generations.

Article by Rosemary Newton, MSBP


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