Why are plants important?
Plants are considered to be the backbone of all life on Earth, with more than 400,000 known species providing a wealth of vital resources and services for both wildlife and humans.
Water is an essential component for all life on Earth, and plants play an important role in helping to distribute and purify the world’s water. Incredibly, the rainforests of the Amazon are thought to store over half of the Earth’s rainwater, acting like a giant sponge. Without these forests drawing water from the forest floor and releasing it back into the atmosphere as swirling mist and clouds which eventually feed into rivers and lakes, devastating droughts would be far more common.
Air and climate
Plants play a critical role in regulating the Earth’s climate, as through the process of photosynthesis they not only produce oxygen but also remove carbon dioxide from the atmosphere. Excessive carbon dioxide production through human activities such as the burning of fossil fuels pollutes the atmosphere, contributing to the negative effects of climate change including rising sea levels and an increasing occurrence of extreme weather events such as hurricanes. By storing excess carbon, plants help to mitigate these negative impacts and keep our air clean.
Food and shelter
Everything we eat comes either directly or indirectly from plants. They form the basis of the food chain, providing nutrition for herbivores which in turn are consumed by carnivores. Plants act as the building blocks of ecosystems, forming diverse habitats and providing shelter for millions of species. In addition, plants are a major source of industrial products such as rubber, resins, fibres, dyes and building materials.
More than a quarter of all modern medicines come from tropical forest plants, and four out of five people around the world rely on plants for healthcare. The anti-malarial drug quinine occurs naturally in the bark of the Andean cinchona tree (Cinchona officinalis). Compounds derived from the Madagascar periwinkle are now widely used in the treatment of a number of different types of cancer. One particular derived compound, vincristine, has been credited with raising the survival rate in childhood leukaemia from less than 10 percent in 1960 to over 90 percent today. There are still many plants whose medicinal properties have not been studied, and many more species still to be discovered.
Soil stabilisation and nutrient cycling
In many habitats the roots of plants help to reduce soil erosion by holding it together, while tree canopies protect the soil from heavy rains. Plants also store vital nutrients and help cycle these through the soil when plant matter dies and decays. If trees are removed from a forest, not only are nutrients lost, but so too is the protection provided to the soil. Unprotected soil is easily washed away, potentially causing floods and triggering devastating landslides.
What threats do plants face?
Unfortunately, these life-giving organisms are facing a whole host of threats, with one in four plants believed to be at risk of extinction globally.
Habitat loss and degradation
It is estimated that habitat destruction as a result of human activity is the principal cause of decline for 83 percent of threatened plant species. A burgeoning human population is sparking an increase in urban development, road building, agriculture and recreation, leading to the destruction and degradation of natural habitats. Studies have indicated that up to two million hectares of tropical rainforest are destroyed each year, which not only devastates the populations of trees being felled, but also those of species which rely upon the rainforest for food and shelter. Magnolia species have been used for more than 5,000 years in traditional Chinese medicine to fight cancer, dementia and heart disease, yet half of the world’s magnolia species are threatened with extinction, principally as a result of widespread deforestation.
Collection and overexploitation
The over-collection and over-exploitation of wildlife is one of the most significant causes of species extinctions. Plants, animals and fungi have been used for food, medicine and other products throughout history, but ever-increasing human populations and advances in the technology required to harvest plants more efficiently have led to the devastation of many species. A certain level of species use is sustainable, but unfortunately many species are harvested or collected at rates which leave the resource unable to regenerate fast enough for the population to survive. For example, the cancer drug paclitaxel is derived from the bark of yew trees, but as it takes six trees to create just one dose of the medicine, growers are struggling to keep up with demand.
An invasive species is one which has been deliberately or accidentally introduced to an area outside of its natural range and which then causes a multitude of problems within the new habitat as it becomes established and dominant. Invasive species often have fast growth and reproduction rates, and the new area often has a lack of natural predators or pests to keep the species in check. In the plant kingdom, invasive species can out-compete native species for space, light or nutrients. One example of this is parrot’s feather, a plant native to Central America which has now colonised shallow ponds in over 100 sites in southern England, threatening the survival of the brown galingale, a native sedge species.
Pollution and disease
Pollution through the release of contaminants into the environment can negatively impact upon plants. Pesticides used on farms to kill off weeds and increase crop yields can have an adverse effect on wild plants if over-applied or misused, and these chemicals also often leach into water supplies, affecting aquatic wildlife. The misuse of insecticide can result in a severe reduction in pollinator numbers, which in turn affects the populations of those plants which rely on these insects to help them reproduce. As a result of acid rain or chemical leaks, soil may become more acidic, affecting which plants are able to grow in that area. Very few plants can tolerate heavy metal contamination, and so the presence of such pollutants can cause several species in an area to die off, allowing only a handful of tolerant plants to thrive.
Deforestation is known to be a major contributor to climate change, being responsible for 18 to 25 percent of global annual carbon dioxide emissions. Carbon dioxide is a naturally occurring gas in the atmosphere. However, as trees are burned to make way for settlements, plantations or agriculture, they release carbon dioxide, and the accumulation of excess levels of this gas disrupts the balance of Earth’s system, leading to increased temperatures and rising sea levels. This problem is further compounded by the fact that large-scale deforestation results in fewer trees available to absorb excess carbon dioxide to mitigate the problem.
Climate change then, in turn, places further pressure upon plants, as well as the wildlife that depends on them for survival. Plants that can tolerate a wide range of habitats and have fast generation times are likely to flourish in a changing environment, but those that are unable to either adapt or move may become extinct. The resultant change in the plant community composition has a knock-on effect for other species, as food webs and the relationships between plants and pollinators are disrupted or broken – if two species which rely on each other for survival no longer live in the same habitat, both may be driven to extinction.
What conservation measures can we take?
With so many threats currently putting the future of plants across the globe at risk, taking conservation action has never been more important. Widely used conservation techniques include habitat restoration, caring for species in botanical gardens, invasive species control and education programmes.
Conservation in the wild
By conserving a species in its natural habitat, natural systems and processes can be maintained.
- Habitat restoration and ecosystem management: This involves managing, maintaining or restoring areas of natural vegetation, while avoiding habitat fragmentation.
- Control of invasive species: After habitat loss, invasive species are the greatest threat to biodiversity, particularly on islands. Through developing and implementing methods to control the spread of damaging invasive species, populations of threatened native species can be given the opportunity to recover and flourish.
- Sustainable use: To ensure the long-term conservation of our most vital natural resources, their sustainable use is of utmost importance. Many people around the world depend on native plants for their survival, and therefore completely stopping the use of these species is impossible. However, by promoting their sustainable use, these plants may thrive and provide for generations to come.
Conservation outside of the natural setting
Should wild populations be decimated, or the natural habitat destroyed, there is a possibility of restoring the ecosystem by introducing cultivated individuals to bolster the natural population. These measures can involve the conservation and maintenance of whole plants, seeds, pollen or tissue.
- Botanic gardens: Botanic gardens are living collections of plants which are carefully cultivated and managed, enabling scientists to carry out in-depth studies, the results of which may prove invaluable in designing and implementing effective conservation measures in the wild. The stock of plants kept in botanic gardens can also act as a basis for the restoration of species in their natural habitat. In addition, botanic gardens provide members of the public with an opportunity to see and learn about a wide range of plants and the importance of plant conservation.
- Plant nurseries: Plant nurseries can be a good method of reducing over-collection pressure on wild plant populations, by providing cultivated plants to be sold to collectors and the general public. The Wollemi pine, a tree species considered to be a ‘living fossil’, is classified as Critically Endangered on the IUCN Red List of Threatened Species, and is one plant currently benefitting from being grown in a nursery.
- Seed and pollen banks: In addition to botanic gardens, seed and pollen banks also play an important role in the preservation of threatened plant species. Seeds can be stored under very specific conditions at extremely low temperatures in what is known as a cryogenic laboratory. As seeds generally do not take up a large amount of space, this method allows large populations to be preserved for a century or more. For species which do not produce typical seeds, pollen can also be preserved for future use or cuttings can be taken and stored.
While efforts outside of a natural setting can certainly play a key role in plant conservation, it is not enough on its own. It is important that such practices reinforce and complement conservation efforts in the wild to ensure the species' future survival.
How to help
- Buy sustainably sourced products: Think about the products that you buy and where they come from and try to buy sustainably sourced products. There are various labelling schemes, such as those run by the Forest Stewardship Council (FSC) and the Programme for the Endorsement of Forest Certification (PEFC), which show that a product has come from a sustainably managed source.
- Buy local: When selecting plants for your garden ensure that it is a native species which will not become invasive if it spreads. If a non-native species is bought, check it is not invasive before planting it in your garden.
- Respect regulations: Introduced species have been the cause of many conservation crises over the years, and while the natural dispersal of invasive plants is difficult to control, the public can play an enormous role in helping to prevent the active spread of potentially harmful species by respecting and observing import regulations when travelling.
- Make your lifestyle greener: Everything we do in our day to day lives emits carbon dioxide into the atmosphere. That means that even making small changes in what we do, or how we do it, can have a positive impact in preventing the onset of climate change. Shop less and try to reduce your consumption, or try walking or taking public transport rather than using a car.
- Support conservation organisations: There are many people working on the front line in conservation that need your support.
- Spread the word: Why not get involved in awareness-raising events or simply encourage family and friends to buy sustainable products, watch out for invasive species or increase their energy efficiency.
Find out more about threatened plants and their conservation:
- Botanic Gardens Conservation International (BGCI)
- Convention on Biological Diversity - Global Strategy for Plant Conservation
- Convention on International Trade in Endangered Species (CITES)
- IUCN Species - Plants
- Millennium Seed Bank Partnership
- Royal Botanic Gardens, Kew - Science & Conservation: Plants and fungi
- SSC Plant Specialist Groups
- World Land Trust