The Fascinating Journey of Plant Migration: How and Why It Happens

How Plants Migrate

Plants migrate in numerous ways, many of which are quite remarkable. We might often hear an older person mention a plant in the area that wasn't there during their youth. Sometimes, humans intentionally transport a plant or seed to a new location when they travel. Seeds can also travel by attaching themselves to a human body or a vehicle, reaching new environments. For instance, cashew trees, originally from Brazil, are now widely cultivated in India and Africa due to the efforts of Portuguese colonizers. Similarly, the rubber tree, native to the Americas, was able to spread across continents and become a valuable cash crop, thanks to human intervention and deliberate actions.

Imagine a different scenario—a seed landing in the ocean. Its fate will be determined by ocean currents, its appeal to marine life, the durability of its outer shell allowing it to float for extended periods without decaying, and similar factors. This is a complex natural process influenced by chance to some extent. The study of plant migration is a significant area within botany. It intersects with fields such as Biogeography, Palaeobotany, Ethnobiology, and human evolution, and is linked to climate and ecosystem changes.

Carriers that Help Plants Migrate

Trees possess natural methods for seed dispersal and migration, such as seeds with wings, seeds with hairs, seeds encased in tasty and juicy fruits to attract animals, seeds designed to roll on the ground, seeds with appealing nuts, and even seeds that can burst out of their pods! Mistletoes and sandbox trees have such exploding fruits. Various insects and small animals bury their collected fruits and often forget them, allowing the seeds to germinate and establish there. While most animals inadvertently transport seeds over distances, humans do so intentionally as well.

How Migrated Plants Survive?

When a seed finds its way into a new habitat, it faces numerous challenges. Have you considered how hard it is for a new plant to gain acceptance in a forest ecosystem? This isn't because forest plants and trees are unwelcoming; rather, it's due to the presence of many perennial trees with well-established root systems. These roots form a network that covers the topsoil, making it difficult for new saplings to establish themselves. Similarly, grasslands, with their extensive yet small-scale root networks, also resist new growth. Migrant plants must also adapt to the climatic conditions of their new environment. Despite these challenges, the diverse plant life found worldwide, regardless of extreme climate variations, demonstrates the resilience of migrant plants.

Transcontinental Migrations of a Little Fern

The ferns migrate over distances comparable to those of a Siberian Crane or an Arctic Tern. Their spores are carried by the wind for thousands of kilometers. Several factors contribute to this extensive migration: the minuscule size of the spores and their capacity to germinate months after being released by the parent fern. Once a spore sprouts, it can develop into a bisexual fern, making reproduction on new terrain effortless.

Story of the Ocean as Told by The Sea Lettuce

Sea lettuce thrives on seashores, with its seeds carried far by the ocean. These seeds can float in the sea for up to a year. Imagine the stories they could tell about marine life if they had a voice! Consider the remarkable tales sea lettuce could narrate about sea creatures, passing ships, and fleeting sunsets witnessed on their journey. After such experiences, the seeds land on a shore, still capable of germinating. They anchor their tiny roots in new terrain. Coconuts and mangrove seeds also embark on incredible sea journeys, seeking opportunities to continue their species.

The Winged Friends of Plant Migrants

Migratory birds and seeding plants share a significant relationship. Birds consume the fruits of these plants and travel to distant regions. The seeds, often with hard outer shells that protect them from digestion, are carried to new locations in the birds' stomachs.

When discussing plant migration, a large category of colonizing species comes into play. These plant species can adapt to various geographies, climates, and have long gestation periods. An example is the Pond Apple, a small tree capable of invading a rainforest and transforming it into a sparse patch of vegetation by forming dense monocultures that suffocate other plants.

Plant Migration by Agriculture

Another aspect of this discussion is plant migration through agriculture. Consider Barley as an example. The earliest known cultivation of Barley originated in the Middle East region known as the Fertile Crescent, dating back 10,000 years. Over time, Barley spread to South Asia, facilitated by the farmers, traders, and travelers of that era. Scientists discovered that a popular Barley variety made its way from South Asia to Europe through human sea routes.

Nature has designed many plants to be pre-adapted for utilizing human migration and activities to spread across the globe. However, introducing a foreign plant to a new environment can pose significant challenges to the ecosystem. Therefore, it is mandatory to obtain special permissions to transport plants from one country to another by sea, road, or air.

Climate change is introducing a tragic new aspect to plant migration. Plants that cannot quickly move from drought-affected areas to regions with adequate water are at risk of rapid extinction. For instance, 80% of the African island, Cabo Verde, is now prone to drought, and authorities are striving to keep the island livable for its human population. In this urgent response to climate change, how much consideration the well-being of the island's plants will receive in policy decisions is uncertain. Particularly concerning is that Cabo Verde hosts hundreds of endemic plant species—plants found nowhere else on Earth—which might be overlooked. Globally, nations are poorly equipped to address the effects of climate change on humans, and other life forms are in perilous situations, facing the threat of extinction unless they can migrate and endure extreme climatic conditions.

References

Encyclopaedia Britannica: Falling Far from the Tree: 7 Brilliant Ways Seeds and Fruits are Dispersed.

Invasive Plant Species of the World, 2^nd Edition: A Reference Guide to Environmental Weeds by Ewald Weber.

On the Origin and Domestication History of Barley (Hordeum vulgare) by A. Badret al., Molecular Biology and Evolution, Oxford Academic.

Plant Migration: The Dynamics of Geographic Patterning in Seed Plant Species by Jonathan D. Sauer.

Plant Migration Studies by Charles E. Bessy.