Human evolution: so dominant we change ecosystems (Introduction)

by David Turell , Friday, April 30, 2021, 18:24 (1085 days ago) @ David Turell

Wherever we invade everything changes; ecosystems alterations on islands:

https://science.sciencemag.org/content/372/6541/488

"Oceanic islands are among the most recent areas on Earth to have been colonized by humans, in many cases in just the past few thousand years. Therefore, they are important laboratories for the study of human impacts on natural vegetation and biodiversity. Nogué et al. provide a quantitative palaeoecological study of 27 islands around the world, focusing on pollen records of vegetation composition before and after human arrival. The authors found a consistent pattern of acceleration of vegetation turnover after human invasion, with median rates of change increasing by a factor of six. These changes occurred regardless of geographical and ecological features of the island and show how rapidly ecosystems can change and how island ecosystems are set on new trajectories.

"Abstract
Islands are among the last regions on Earth settled and transformed by human activities, and they provide replicated model systems for analysis of how people affect ecological functions. By analyzing 27 representative fossil pollen sequences encompassing the past 5000 years from islands globally, we quantified the rates of vegetation compositional change before and after human arrival. After human arrival, rates of turnover accelerate by a median factor of 11, with faster rates on islands colonized in the past 1500 years than for those colonized earlier. This global anthropogenic acceleration in turnover suggests that islands are on trajectories of continuing change. Strategies for biodiversity conservation and ecosystem restoration must acknowledge the long duration of human impacts and the degree to which ecological changes today differ from prehuman dynamics.

"Globally, human activities dominate ecological systems (1, 2) and are considered the main drivers for accelerating contemporary ecosystem transformation.

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"...ecological legacies of human arrival on islands may persist for centuries and are often irreversible. An example is Tawhiti Rahi in the Poor Knights archipelago, which is currently uninhabited (19). Immediately after initial arrival by Polynesians in the 13th century, the island’s forest cover was cleared by fire for human habitation and gardens. After a massacre of local Ngatiwai inhabitants on Tawhiti Rahi in 1820, local kaitiaki (guardians) declared the islands wahi tapu (protected by a sacred covenant), after which time there was no subsequent settlement. Despite the island becoming totally reforested within 150 years, the current forest composition is completely different from that of the prehuman period. In contrast to the Poor Knights archipelago, most currently inhabited islands have experienced at least two distinct waves of settlement, each having distinctive signatures of change and leaving increasingly complex legacies

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"Our results show little indication that these human-affected ecosystems are either similar to or returning to the dynamic baselines observed before human arrival. Therefore, anthropogenic impacts on islands are lasting components of these systems typically involving initial clearance (e.g., using fire) and are compounded by the introduction of a range of introduced species and extinctions of endemic species and ongoing disturbances. This contrasts with turnover after natural disturbances in the prehuman period, when island ecosystems often recovered rapidly to predisturbance states."

Comment: The importance of ecosystems cannot be overemphasized. Living organisms naturally form cooperative systems and our overall dominance upsets them with plant systems, animal systems or combinations. We have severely affected the Earth's evolution.