What lies ahead for orchids in a changing climate?

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Climate change is a phenomenon that affects all living beings equally. It refers to the long-term shifts in temperatures and weather patterns. The factors that drive climate change can be natural; such as changes in solar cycles and volcanic activity. However, in recent times the main driving force of climate change has been rampant human activities. Sudden climate change results in a wide range of fluctuations in the natural environment, including frequent wildfires, increased droughts, rising sea levels, and other alarming outcomes such as a severe loss of biodiversity. It is, therefore, of no surprise that Orchids, one of the most sensitive angiosperms, find themselves threatened by climate change today.

What are orchids?

Orchids are highly advanced plants. Orchidaceae is one of the two largest families of flowering plants, with over 27,000 species of orchids spread around the world. These plants are found on every continent except Antarctica. Orchids are widely distributed in tropical, subtropical and temperate biomes. These plants are mostly epiphytes and grow on the surface of other plants for support.

For years, orchids have been a subject of interest for botanists and evolutionary biologists all over the world. Orchids exhibit a wide range of morphological and ecological diversity. These flowers are highly valued on the global horticultural market and possess a multi-billion-dollar commercial worth in international trade.

Orchids are vibrant plants. They interact with their environment extensively and are indicators of the health of the ecosystem. They depend on mycorrhiza for germination, and pollinators like insects for their propagation. Thus, the complex life cycle of orchids and their intricate interactions with fungi and pollinators make them particularly vulnerable to climate change and human activity. An understanding of these complex interactions is essential in developing effective conservation strategies.

Does climate changes have any positive impacts on orchids?

Climate change at natural rates over decades is normal for life on earth. Dynamic tectonic shifts and gradual climate change is considered to be related to the diversification and speciation of orchids.

Studies have indicated that sea level fluctuations are the main driver for divergence and diversification of moth orchids. Research on Dendrobium has shown that its diversification is related to the plate motions and the alternation of glacial and interglacial stages of the Earth. CAM (Crassulacean Acid Metabolism) is an important photosynthetic pathway in which CO₂ is taken up at night and temporarily stored as malic acid in cell vacuoles. Malate is liberated from the vacuoles and decarboxylated during the day. The origin of CAM in Dendrobium was associated with a pronounced climate cooling followed by a period of aridity.

Climate change brings about sea-level fluctuations, resulting in the isolation and junction of any two islands or island and mainland bodies. This enables great diversity of orchids in a limited area.

However, global warming, a consequence of drastic climate change, begets frequent extreme events and impact the orchids’ adaptation, hence aggravating species extinction.

What about the negative impacts?

Consistent threats to orchid diversity has landed many species of these floral wonders in the IUCN Red List of Threatened Species (International Union for Conservation of Nature).

Threats to orchids increase with the rising popularity of these flowers among collectors. Factors such as land clearing, habitat destruction, fragmentation of habitat, increased susceptibility to fire threat, pollinator decline and climate change make them the most often threatened plants.

Habitat degradation due to climate change is a major concern

Orchids have specific habitat requirements, the lack of which leads to their rarity. Unpredictable rainfall and evaporation rates will cause imbalance in soil moisture, vegetation and microclimates of these habitats. This has large impacts on the terrestrial orchid population. Extreme rainfall can accelerate soil erosion. Increased degree and frequency of soil erosion negatively affects the plant population in hills.

Orchids show high dependency on selected species of fungi, plants and animals. The symbiotic relationship between orchid species and mycorrhizal fungi is crucial for natural seed germination, seedling growth, post-seedling growth and nutrition of all orchid species. Environmental factors in turn influence the function and stability of orchid mycorrhiza.

Climate Change impacts orchid-pollinator interactions

Some orchids are highly species-specific with regard to attracting pollinators, thus developing complex mechanisms for the pollination process. This results in the restriction of orchid distribution to that of its specific pollinators. Increase in temperature and CO₂ levels adversely affect flowering period of orchids. Early or late flowering affects orchid pollination, and thus affects its propagation. The unusual flowering fails to attract insect pollinators, which in turn, decreases orchid population.

Higher temperatures coupled with low precipitation due to climate change tends to cause more forest fires, killing all flora and fauna in the area. Frequent forest fires leads to extinction of local species.

Epiphytic orchids have tight associations with the host plants they rely on, thus limiting the total orchid distribution to that of their host. Severe frost in winter followed by extreme dry spells in spring can cause drying of epiphytic orchids in the host plant.

Rise in temperature gives rise to a difference in cloudiness, resulting in the hampering of orchid populations. Global warming also affects orchids in mountain tops. Many orchids in the upper forest canopies are sensitive to desiccation (drying out), which is brought about by global warming.

How can orchids be conserved in a changing climate?

A number of strategies can be adopted to conserve orchids from the threats that climate change possesses:

Restoring and maintaining native ecosystems

Existing ecosystems can be restored by afforestation and reforestation, inclusion of new plant species and strict measures to prevent the loss of existing species. Reintroduction can also be a suitable option.

Managing habitat for species under threat

Many rare plants can be conserved by keeping their native habitats healthy. Periodic monitoring makes sure that rare plant populations are still thriving. This can ensure their long term survival. Proper habitat and ecology maintenance is the best hope for orchid conservation. In the case of rare orchids which require specific pollinators, multiplication outside, replanting of the orchid in suitable areas and monitoring of pollinators can be a viable solution for conservation.

Seed storage and banking

Storing orchid seeds is a good option during alarming climate change situations. These seeds can maintain viability in subzero conditions. Cryopreservation of seeds is also good option for storing seeds for longer periods of time. This can lead to an increase in the germination ability of orchids. In-depth research is required to determine appropriate moisture and temperature levels for seed storage to ensure longevity of the seeds to be stored. Domestic freezers can be used for seed storage.

Cryopreservation of seeds.

Strict vigilance

Strict vigilance and constant surveillance by government agencies, NGOs, village communities, etc. is essential for protecting existing rare orchids.

Conclusion:

Orchids are vibrant angiosperms that show immense diversity in their morphology and in the habitats in which they occur. They are responsible for maintaining ecological balance in their respective niches, especially with regard to the different pollinators and mycorrhiza species they are associated with. Orchids are also of immense economical value due their beauty.

Climate change has become the primary concern for environmentalists all around the world. In a time when anthropogenic activities are accelerating climate change, learning more about these plants and conserving them to maintain intricate ecological balances is essential.

Written by: Sivani Y.S.K.