Melbourne, Aug 14 (The Conversation) Pollinators are crucial for fertilising flowers, which subsequently mature into seeds and fruits, playing a foundational role in agriculture. However, climate change can disrupt the synchrony between plants and their pollinators, influencing their habitats and periods of activity. This phenomenon isn't new.
During a rapid global warming phase 56 million years ago, plants and their pollinators from arid tropical regions ventured into new territories. Our recent study, published in Paleobiology, reveals this significant shift happened in a remarkably brief span of just a few thousand years.
Could historical climate changes shed light on how plant-pollinator interactions have evolved? This was the focus of our investigation.
A historic warming episode 56 million years ago In the past 150 years, human activity has pushed atmospheric carbon dioxide levels up by over 40%, contributing to a global temperature rise exceeding 1.3°C.
Current levels of greenhouse gases and global temperatures aren't just unprecedented in human history; they surpass any point in the last 2.5 million years.
To understand the potential impact of significant carbon emission events comparable to ours, we must look farther back into Earth's history.
Fifty-six million years ago, a sudden warming event, driven by substantial carbon release into the atmosphere and ocean, occurred. Known as the Paleocene-Eocene Thermal Maximum, this event warmed the Earth by about 6°C for over 100,000 years.
This massive carbon discharge, though slower than today's climate change, profoundly affected Earth.
Previous research indicated significant shifts in flora and fauna during this period, mostly evident in their geographic distributions. We explored whether pollination dynamics were influenced by this rapid climatic shift.
Exploring ancient pollen in the badlands Our focus was fossil pollen from Wyoming’s Bighorn Basin, a vast valley in the northern Rocky Mountains loaded with sedimentary deposits from 50 to 60 million years ago.
The expansive modern-day badlands of the Bighorn Basin reveal sediments rich in fossils, left by ancient rivers eroding the surrounding heights.
Fossil pollen offers insights into historical pollination changes due to its abundant, widely dispersed nature, and resilience to decay, making it well-preserved in ancient rocks.
We employed three investigative approaches to study pollination in the fossil record: pollen preserved in clusters, pollination methods of living plant relatives, and the diversity of pollen shapes.
Our discoveries Our analyses highlighted a rise in animal-assisted pollination corresponding with heightened temperatures and carbon dioxide levels, while wind pollination decreased.
Wind-pollinated species included those related to the broad-leaved deciduous trees prevalent in today's moist temperate northern regions.
Conversely, animal-pollinated plants were akin to subtropical palms, silk-cotton trees, and other vegetation typical of dry tropical climates.
The decrease in wind pollination seems linked to the local extinction of wind-pollinated plant populations in the Bighorn Basin.
The surge in animal-pollinated flora indicates a poleward spread of plants from warmer, drier regions into the Bighorn Basin.
Earlier studies tied these botanical changes to the hotter, more seasonally dry climate of this rapid-change period.
Pollinators, including insects and other animals, likely relocated with the plants they favored 56 million years ago, facilitating the establishment of new plant communities in the warm, arid climate. These communities likely offered vital resources to early primates, marsupials, and other small mammals.
Lessons for the future What insights can we glean from this ancient climate change event for our trajectory today? The initial Paleocene-Eocene Thermal Maximum carbon surge prompted substantial global warming, significantly altering terrestrial and aquatic ecosystems.
Despite these drastic shifts, most terrestrial species and their ecological networks endured, likely due to the event’s slower pace compared to current anthropogenic climate changes.
Following over 100,000 years of a hot, drier climate, the returning forests were much like those present before, suggesting forest ecosystems and their pollinators can re-form similar communities post prolonged climate changes, provided major extinctions don't occur.
The lesson for the future lies in managing the rate of environmental changes to prevent extinctions. (The Conversation) SCY SCY
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