Tracking environmental change to save biodiversity and languages from extinction

Prepared by: Valentina Delconte (OpenGeoHub),

Insights from OpenGeoHub’s seminar series “Biodiversity: how big is our global biodiversity debt and what can we do about it?” on December 23, 2021.

To help us answer the question: “Can nature keep up with human-induced environmental changes and can ecosystem regeneration be enough to save our Planet?” we invited two biodiversity experts Dr Kenneth Rijsdijk, Island Biogeography researcher for the Institute of Biodiversity and Ecosystem Dynamics at the University of Amsterdam and Dr Sietze Norder, Postdoctoral Researcher at the Leiden University Centre for Linguistics.

Learning from 100,000 years of Earth’s history

Islands ecosystems offer early glimpses, being at the front lines of global change. They are threatened by habitat loss and degradation, overexploitation, and changing ecological networks (including invasive species) with the loss of unique species and human cultures.

Extinction is part of life. It’s part of Earth’s history” points out Dr Rijsdijk. In a time-lapse of four and half billion years, much before the arrival of human species, living creatures on Earth were wiped out five times during mass extinction events, with more than 75% of families and species lost due to extensive changes in environmental conditions. Whilst there are many culprits for mass extinction events, from climate change, continental drift, volcanoes to meteor impacts and even loss of oxygen in the oceans⁠ — one thing is for sure⁠ — they fundamentally change the path of evolution.

In many ways, we are only just beginning to understand mass extinctions, yet here we are as a species faced with the sixth mass extinction. Ecological and geological processes have been shaping life on Earth for millions of years removing and regenerating vast habitats for diversity on land.

One of the fastest and most large-scale natural transformations has been determined by sea-level rise: since the last million years sea levels fluctuate with a period of ca. 120,000 years between -135 m and up to +10 m compared to the current sea level (Mean Sea Level — MSL), with a rate that peaked at 40 m/ ky (1000 years) continues Kenneth: “After the last Ice Age, sea level started to rise up to more than 30 meters per millennium in total: you can imagine that a lot of tropical forests on the coastline became flooded, and was lost, and many islands became smaller.

Watch the Biodiversity webinar here: https://doi.org/10.5446/56062.

In 2005, a Dutch and Mauritanian team of paleontologists, among which Kenneth, uncovered the widest extinct-bird dodo’s mass grave of the area of two football fields at Mare aux Songes, a swampy area near a sugar plantation on the south-east of the Mauritius Island, South-West Indian Ocean. Mauritius Island is most famous among conservation biologists for having gifted the world with the very symbol of human-induced species extinction, the iconic dodo (Raphus cucullatus). But what drove the flightless bird to extinction was long misunderstood.

We discovered that of all kinds of animals that are present [in the mass-grave], about half of the species we discovered were extinct” recalls Kenneth, without surprise in his voice.

Island size reduction and distancing must have induced pressures, especially on terrestrial insular ecosystems, inducing upward migrations and interspecies competitions, and possibly extinction, following 1967’s acclaimed MacArthur and Wilson island biogeography theories. Yet, at the end of a few million years characterized by a slow, but constant land loss after the last ice age and harsh climatic extremes, evidence showed that dodos and other endemic species of the Mauritius islands adapted and survived as “the rate of change was not so high to cause extinction.”

Particular conditions on islands have made organisms disproportionately vulnerable to anthropogenic pressures such as habitat loss, overexploitation, invasive species, and climate change. A recently published Scientist’s warning paper highlights that 75% of all extinctions worldwide were island species. From: Fernández-Palacios et al., 2021.

During our webinar, Kenneth shows how the 6-year-long excavation on Mauritius represented something more than just a memorial for an extinct bird: it could give a glimpse of the effects of humans on ecosystems and how the anthropogenic changes had impacted the biodiversity of the island.

The example of Kenneth’s study can provide a clearer perspective on the dodo’s fate, indicating the arrival of humans as the main driver of the quickest extinction event ever recorded, attributed to rapid deforestation, constant soil erosion and the introduction of pests and alien species which pushed native inhabitants to the brink of extinction.

Dutch sailors were the first stable inhabitants of the Mauritius islands. The need for food, land and natural resources led the settler population to modify the surrounding environment over the course of the centuries. The modeled soil loss has been classified into three classes: low loss (0–2 tons/hectare/year) in green, moderate (2–12.5 t/ha/yr) in orange, and high (> 12.5 t/ha/yr) in red. Image retrieved from Norder at al., 2017.

Many studies agree upon the fact that forest clearing — in combination with the impact of invasive species and overexploitation — is a major cause of biodiversity loss on islands, and the 2020’s Living Planet Report by the World Wildlife Found indicated habitat loss and exploitation are among the primary threats to land and water biodiversity. Additionally, on islands the impact of land use/land cover change on biodiversity is higher than on continents, and native vegetation cover across islands worldwide has vastly reduced following human colonization.

“We don’t know what was the loss rate of biodiversity on the island, but what we know is that the rates of human-induced change exceeded the ecological recovery of natural forest.” concludes Kenneth, “the dodo was unique to Mauritius” and once the endemic bird was eliminated from its only habitat, we lost a species forever.

Islands of diversity: languages and cultures

It’s the study of the biogeography of Mauritius islands and many other archipelagos that brought Kenneth Rijsdijk to work with Sietze Norder, author of the recently-published book on island biodiversity called: The World in Miniature that traces the rise and fall of island civilizations, and the emergence of novel ecosystems, languages and cultures.

Surprisingly, biodiversity and cultural diversity are more connected than we might think at a first glance. Hotspots of biological and cultural diversity are often found in similar locations, remarks Sietze, whose studies show patterns of biological and cultural diversity have been shaped by interactions between climate, topography, and ecology. After his doctoral degree in island biogeography in the Anthropocene and Quaternary, Dr Norder is now focusing his work on the application of methods and theories from biogeography to patterns of human cultural diversity and migration (by creating, for example, the R package for linguistic mapping Glottospace).

The Map of Linguistic Diversity was created by the University of Wisconsin Oshkosh’s Kazimierz J. The index of linguistic diversity is a number ranging between 0 and 1, i.e. a country where many different languages are spoken will have an index closer to 1, while a country where very few different languages are spoken will have an index closer to 0. Image source: https://www.articque.com/cartes-de-kazimierz-j-zaniewski/.

Just as for biodiversity, the environmental settings of an island, including area, really explain the pattern of cultural diversity” follows Sietze. For instance, a major factor that could explain Indonesia’s 711 different languages is its geography — Indonesia is made up of 17,500 islands (although more than 7,000 of them are uninhabited)!

Island are precious pockets of cultural diversity, preserving:

  • 27% of human languages;
  • 25% of critically endangered languages;
  • 50% of endangered languages.

With each subsequent generation, it’s becoming clearer that the declining patterns of global biodiversity are also affecting human cultures: the global variation in languages has seen a rapid loss over the past century, surpassing the loss of birds and mammals. Of the roughly 7,000 languages spoken on Earth today nearly half are currently at risk of being forgotten, most of which are endangered indigenous languages, according to the United Nations Educational, Scientific and Cultural Organization (UNESCO). A striking example was brought by the case of Boa Sr, an indigenous elderly of the Andaman Islands, whose death in 2010 marked the loss of the last Bo language fluent speaker.

Watch the Biodiversity webinar here: https://doi.org/10.5446/56062.

While each language is subject to specific social, demographic and political pressures, there are some common drivers threatening the linguistic mosaic of our Planet. Contrary to what one could expect, preservation of languages is not particularly endangered from the contact with other languages, but rather from greater road density, which may encourage population movement and higher average years of schooling-evidence that formal education can contribute to the loss of language diversity.

Without intervention, language loss could triple within 40 years, with at least one language lost per month […] loss of over 1500 languages by the end of the century, which correspond to 20% of global language diversity” — Bromham et al., (2021).

Restoring those lost relationships

In just the last 40 years, human-induced deforestation and land conversion caused the loss of the same area flooded by sea level rise in the tropical zone over 18000 years of a post-glacial era -concluded Kenneth. At the same time, agricultural practices accelerate soil erosion to a point where what takes 100 years to form is lost in one intense rainfall. Such rapid and profound changes are “ so hard to believe” for biodiversity experts.

Nature takes it slowly (in our perspective) to go from barren rock to diverse ecosystems. Natural ecosystem creation rates require time-spans much beyond the human time scale, and just to give an example 1 cm of mineral soils takes around 100 years to form (this is the average rate of rock turning into soil). And once the mineral soil is eroded away, it can take centuries to form entirely new soils from the underlying rock. It is far quicker to restore what is degraded before it is completely lost. Soil is, after all, critical to forming rich, diverse and resilient ecosystems. The complex web of interactions between species is much quicker to regenerate and repair, than it is to evolve from bare rock and shifting sands again. Relationships between species are the very thing that defines the resilience of an ecosystem: the more there are, the more the system can adapt to perturbations and resist total loss of function.

However, an average of 68% of monitored populations of mammals, birds, amphibians, reptiles and fish declined between 1970 and 2016, making us wonder if the Earth’s sixth mass extinction is already here. Although the current rate of species loss is unprecedented, the magnitude of the extinction is not yet at that of past events, as Sietze remarks, believing that this gives us a unique opportunity to revert trends and restore a thriving Earth’s biosphere.

As demonstrated by the work of these two Dutch scientists, island research has produced numerous examples of how understanding long-term human-environmental interactions and legacies of land and sea use through indigenous languages can help guide future resource management: “Mauritius Island is a beautiful example of integrated conservation projects”, recaps Kenneth.

The integration of field sampling with machine-learning-based modeling of trends in life and language diversity has been central in Kenneth’s and Sietze’s works and can provide novel, cost-effective and timely tools in addressing island conservation and regenerations efforts in light of today’s crises. At the same time, ecosystem restoration, sustainable land management, and integrated conservation practices are considered key strategies to address climate change and the biodiversity crisis. However, when species are introduced in sub-optimal conditions, and without enough resources to monitor trends, they may turn into initiatives that do more harm than good. Local communities and landholders are key players in Earth’s restoration and they should lead the decisions aided by accurate and accessible data on their lands: what if advanced AI could tell us where to plant a tree with a nearly 100% chance of success for almost no costs? Could we restore those lost relationships?

Existing machine-learning derived maps tracking Earth’s biosphere and cultures are able to provide us with the tools to estimate the effects of humans on ecosystems in the future: if we know this, we can adjust policies and practices timely, and reshape the way we live on our diverse planet.

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