Seed banking protects native plants from future perils.

By B. Naqqi Manco, Senior Conservation Officer, Turks & Caicos National Trust

Deep inside an underground fortification, with thick concrete walls, little light, and frigid temperatures, something sleeps. The slumbering one lies with others of its kind, waiting . . . and they may wait for a year, or ten, or hundreds. Theoretically, they may sleep for several thousand years. Most ideally, they will never have to be awakened, but if they are, their work will be vital to the survival of their kind.

The sleepers are the amazing distance and time travellers of the plant world — they are seeds. The deep fortress that defends their sleep is the Millennium Seed Bank in West Sussex, England. Founded by the Royal Botanic Gardens, Kew, at their Wakehurst Place site, the Millennium Seed Bank was developed with the aim of long term conservation of 10% of the world’s plant species by the year 2010. Comprising laboratories and offices on the ground level and seed vaults below ground, the facility receives seeds from all over the world and cleans, tests, and stores them for the future protection of thousands of plant species.

Cockspur tree

The Seed Bank has sent several representatives to the Turks & Caicos Islands over the years that the Turks & Caicos National Trust has worked with the Royal Botanic Gardens, Kew on collaborative projects. In 2008, with a grant from the Millennium Seed Bank, the Turks & Caicos National Trust embarked on a six month seed collection project aiming to collect and bank 75 species of plants native to the Turks & Caicos Islands — less than 20% of our native plant species, but still ambitious.

Humans have been collecting and storing seeds for millennia. Seasonal crops are stored between growing times as seeds. Seeds are kept as medicines, talismans, jewellery, and even toys. Seeds that we eat as staples, which we call grains, must be protected from insect pests, water, light, mould, and other damage. Modern agriculture has adapted to the fragility of seeds, and agribusiness now makes sure that seeds are kept in     vacuum-sealed light-proof pouches, treated with fungicide, and distributed at the proper growing times. The survival of our food plants is ensured, long-term, by our very own need to survive.

But humans have not yet unlocked the helpful potential of most plant species. Many, due to our own ignorance, are considered useless. While about 80% of our modern medicines are plant derivatives, we find it easier to produce them in laboratories and manufacture them into capsule form than to grow, harvest, and process the raw plants. Before the Industrial Revolution, most of our colouring agents were plant-sourced, but modern chemical dyes have made many plant-sourced dyes fall from popularity. And even though scientists ever discover new, and potentially life-saving, alkaloids in plants, we often ignore the plants under our feet without thinking that they may have a use far beyond our scope of understanding.

One such plant whose uses have largely evaded global culture thus far is the National Flower of the Turks & Caicos Islands, the Turks & Caicos heather Limonium bahamense. Small, tough, and understated, this plant displays a subtle, stoic beauty to anyone who looks close enough. It stands out in its habitat only because it grows where other plants cannot — on rocky, salt-encrusted mud along the salinas and salt marshes of several islands in the Turks & Caicos. These few spots, many threatened by development of the constant dredging and filling of swamps for human use, comprise the entire worldwide range of this species. It exists nowhere else on Earth. Populations are known on Grand Turk, South Caicos, and Big Ambergris Cay; more recently it has been found on Middle Caicos as well. Salt Cay is certainly its centre of distribution, where it takes advantage of both the salina walls and low, salt-sprayed rocky hills of the island — habitats that stunt and kill most other plants. Turks & Caicos heather lives where it lives because it can tolerate salt, drought, and low nutrient levels; it also lives where it lives because it cannot compete with larger plants in other habitats. It also cannot compete with human development, which is rapidly reducing its available habitat.

Many plants, like the Turks & Caicos heather, face threats from human activity. People over-harvest trees for charcoal, burn vegetation for agriculture, introduce exotic pests and diseases that kill native plants, and bulldoze or bury plants that are simply in the way. Plants cannot relocate themselves — the price they pay for the ability to derive energy directly from sunlight is their locomotion.

Endemic Caicos Orchid is found nowhere else on earth

Individual plants have no ability to run away from danger, but they do have a way to move. Most plants produce seeds as their progeny. Seeds are typically small, well-protected, and contain everything needed to make a new plant. Seeds come in all shapes and sizes. The smallest seeds belong to orchids, and consist of very little besides a genetic code in a papery husk — they can float on the slightest air current to travel thousands of miles (the common monk orchid Oeceocades maculata, originated in Madagascar but travelled, on its own, to the Caribbean — including the Turks & Caicos Islands — on hurricane winds through the past century). The largest seeds belong to the palms, and while they cannot fly, they can float on sea currents for thousands of miles. Seeds have wings, parachutes, floats, sticky barbs and spines, hooked hairs, droplets of gluey resin, and other adaptations that help them travel to new locations by wind, water, and animal power. Some plants produce seeds in fruits that are explosive or ballistic — the Mediterranean squirting cucumber can blast its seeds in a jet of juice several metres away.

Many seeds not only travel physically, but also have the ability to travel temporally. If conditions are not suitable for the seed to grow, it simply lies dormant and waits until the right conditions occur. But in today’s world, seeds are almost as likely to land on a paved road and get washed into a drain to their demise as to end up somewhere ideal to grow. Wild habitats are shrinking as humans consume more land for development. Pests and diseases from far-off lands, accidentally imported by human activity and against which native plants may have no defence, threaten a sprouting seed. Drawing on an idea as old as agriculture, scientists around the world began working collaboratively several decades ago to create seed banks — repositories for seeds that would hedge against the extinction of plant species should disaster befall the growing plants.

Storage can be done with any seed that can dry out and be triggered back to life by the right conditions. Such seeds, which comprise most plant species, are called orthodox seeds. Orthodox seeds can be put through the necessary processes for seed banking, and survive in the seed bank conditions — some have estimated dormant lifespans of thousands of years. Orthodoxy is one of the first determinations that must be made before seeds are collected, a process that begins in the native range of plant species.

Collecting seeds from the Turk's Head Cactus

To start the collection process, botanists from the Royal Botanic Gardens, Kew and the Turks & Caicos National Trust teamed up to create a target list of species to collect. Using the master plant list of the Turks & Caicos Islands, the team first removed species of plants which are known not to produce orthodox seeds. The Agave century plants, Zephyranthes rain lilies, and most palms bear seeds that are recalcitrant, meaning they must be planted while still fresh and moist, and so were not included as targets. The team then focused on priority plants — most notably, plants endemic only to the Turks & Caicos Islands and southern Bahamas. These were classed as high priority collection targets, as were ecologically important native plants. Some native plants were made a lower priority simply because the numbers needed to bank seeds — 10,000 seeds is the ideal — would just not be available due to some plant species’ determined lack of fecundity or their rarity in the Islands.

The collection process begins with locating an appropriately sizeable population of plants producing seed (or fruit containing seed). The seeds are examined by hand for ripeness (to make sure they’re mature enough to collect), damage (to make sure they’re not filled with beetle grubs or mouldy inside), and fertility (to be sure they’ll actually grow). This is usually done by slicing a few seeds open and checking for healthy food reserves and plant embryos; this also gives the collector a chance to estimate how many seeds are in each fruit and thus how many fruits must be collected for the target amount. Unripe seeds are noted for later collection. This can be a tricky proposition, as some fruits ripen by bursting open, scattering the seeds hither and yon, impractical to harvest. In other cases, a plant may ripen its fruits perfectly, but the team may return to discover that the entire harvest has already been made by birds and lizards!

When the right conditions for collection are found, seed collector Melanie Visaya and team members first collect an herbarium specimen of the mother plant. This pressed, dried plant acts as a voucher for the team’s identification in the future. The location of the population is logged by GPS, and its size is estimated. Seeds are then collected into bags, but the team will strive to remove no more than 20% of the available seed from the plants. This ensures that plenty of seed is left behind to interact with the ecosystem’s food web as intended by nature.

Seed collection itself is simple. One team member likened it to the primeval practice of the “gathering” aspect of hunter-gatherer peoples. The practice is very natural-feeling and after several minutes becomes almost soothing and mesmerising. I’d choose fruit-picking over throwing a flint spear at a woolly mammoth any day.

When bags of fruit or seed are collected, they are transferred to the Middle Caicos Conservation Centre, where the herbarium specimens are dried and the fruit is laid out in cardboard trays to dry it as well. Fleshy berries, which go mouldy quickly, are sometimes cleaned by hand by squashing and washing in water. Fruit capsules that dry and pop open are covered with newspaper to prevent the all-too-familiar “ping” of seeds flinging forth from ballistic capsules, rattling across the laboratory floor. Some fruits, such as those of the southern Bahamas and TCI endemic Britton’s Hibiscus Hibiscus brittonianus, are covered with highly irritant hairs and are cleaned outdoors with protective clothing. Other fruit, due to its irresistible flavour to insects or rodents, must be dried inside the lab to prevent predation. A few offer pleasant surprises — the TCI and Bahamas endemic “stinky bush” Eupatorium lucayanum fills a room with a deliciously gentle minty-lavender scent as its fruiting heads dry. Others, such as the sea lavender Argusia gnaphallodes, created such a stench of rotten fish that they had to be exiled to an outdoor patio.

When the seeds are fully dry, they are packaged for shipment to the United Kingdom. After TCI export permits, UK import permits, and other paperwork is in hand, the seeds are shipped by courier, with their respective herbarium specimens and collection data, to the Millennium Seed Bank. There, technicians will clean the seed professionally in laboratories. Many fruit juices inhibit germination (the plant doesn’t usually want its seed growing while still inside the fruit) so they are cleaned thoroughly of juices and fleshy parts. Husks and capsules are removed, and parts are fully dried in special dry rooms so that all that remains is clean, dry seed.

The seeds then go through a quality control process that literally weeds out the unfit. Some are cut open to re-check fertility and pest damage. Groups are X-ray scanned to reveal hidden flaws or pests. A selection will be sterilised and planted on sterile agar in a clean room to test their germination rates and ratios. Meanwhile, the herbarium specimens are reviewed by plant family experts to verify the identifications. Most amazingly, while all of this work is happening, it is being observed by Wakehurst Place garden visitors. The entire Millennium Seed Bank workspace is bisected by a large exhibit hall with glass walls, so that all parts of the seed banking process are fully visible to school groups and garden visitors.

When a batch of seed passes this series of examinations, it will be sorted into containers, labelled, and taken down to the Millennium Seed Bank’s lower level. There, it will be filed into one of the many cold storage facilities which are held at a constantly low humidity and below-freezing temperatures. Here, the seed sleeps. It is only awoken if its country of origin needs it. The Millennium Seed Bank does not sell, trade, or gift seed without the expressed permission of the country of origin.

There, as of November 2009, collections from over 100 native Turks & Caicos Islands plants are held in conservation storage. The Seed Bank has been compared to Noah’s Ark; a time-travel ship with a hold of precious reproductive cargo intended to safeguard species against extinction. The seed bank now holds collections of all known island populations of Turks & Caicos heather, as well as several other endemic plants such as Britton’s buttonbush Borreria brittonii. Another national symbol, the Turk’s Head cactus, is protected there. In a dizzying regret of hindsight, the project began after the attack of the pine scale insect on the Caicos pine, and pine seeds have not yet been banked. This is exactly the sort of future threat, though, against which numerous native plant species are now protected due to their seed having been banked.

Not all seeds can be banked. Some seeds must be planted while they are still fresh and moist. A coconut is a seed, but try planting one that has lost its water reserves or has been frozen, and you would be wasting your time. Many palms and other plants are similar — their seeds cannot grow once their insides have dried through. These non-bankable seeds, which are referred to as recalcitrant seeds, pose a special conservation challenge that seed banking cannot meet. They remind us that while conservation storage of seeds is an excellent safeguard against extinction of some species, it is the wild habitats that must be preserved to prevent extinctions on the long term scale. Noah’s Ark is a good analogy for seed banking, but we must assure that there is somewhere for the ark to come ashore for its sleeping splendour to grow, thrive, and bloom for the future.