A Model for Modern Biodiversity and Rewilding

How Early Farming Enhanced Biodiversity Lessons from Early Human Agriculture for Modern Conservation

Insights from Early Human Agriculture

In a time where news of species extinction is all too common, the role of human activity in shaping biodiversity is under intense scrutiny. Since AD 1500, over 705 vertebrate and 571 plant species have vanished, with human land use being a major culprit. However, research¹ into early farming practices reveals that ancient agricultural activities often enhanced rather than diminished biodiversity. This surprising finding offers valuable lessons for contemporary conservation and rewilding efforts.

The Long History of Human Impact

Humans have been altering landscapes for hundreds of thousands of years. Evidence suggests early humans burned the African savannas as far back as 400,000 years ago, with Neanderthals influencing European vegetation around 125,000 years ago. Additionally, human activity likely played a crucial role in the extinction of Earth's megafauna over the past 100,000 years.

Relationships shown are for those biomes within North America (left-hand panels) and Europe (right-hand panels) that met the inclusion criteria, encompassing the period 8,000–100 cal yr bp (Methods). Lines represent median fits across 1,000 resamples; shaded intervals represent interquartile ranges across 1,000 resamples. Note that anthropogenic land use is back transformed. Heterogeneity is calculated by Bray–Curtis. Diversity axis ranges are consistent within but not between continents. Grey land surface areas are not considered. NA tundra n = 872, EU tundra n = 1,016, NA boreal forests/taiga n = 1,725, EU boreal forests/taiga n = 1,704, NA temperate conifer forests n = 3,204, EU temperate conifer forests n = 3,816, NA temperate broadleaf and mixed forests n = 5,002, EU temperate broadleaf and mixed forests n = 22,666, NA temperate grasslands, savannas and shrublands n = 1,242, EU Mediterranean forests, woodland and scrub n = 2,834.

About 12,000 years ago, the end of the last ice age marked the beginning of the Holocene epoch. This period saw humans transition from foraging to farming, dramatically altering their environments. This shift, encompassing rice paddies in China, wheat fields in the Levant, and maize and squash cultivation in Mesoamerica, led to significant modifications of the landscape and the domestication of livestock.

Fossil Pollen and Vegetation Change

To understand how vegetation has evolved over millennia, scientists study fossilized pollen grains found in sediment layers of peat bogs and lakes. These pollen records provide a detailed picture of plant species diversity over time. Analysis of data from the Neotoma Paleoecological Database shows that plant diversity increased across most of the northern hemisphere during the Holocene, starting around 9,000 years ago in Europe. Surprisingly, these increases often coincided with rising human activity.

In contrast, the southern hemisphere presented a more varied picture. In Africa and South America, increased human land use correlated with decreased plant diversity, while reduced land use saw an increase in diversity. Despite this, the turnover rate of plant species—how quickly different plants replaced each other—increased with human land use across all continents, highlighting humanity's long-standing role as a driver of vegetation change.

Farming and Patchy Landscapes

After the last ice age, warming climates led to the spread of forests across thawed northern lands. These expanded forests saw the strongest links between human activity and increased plant diversity. Conversely, in open and grassy regions like the North American Great Plains and African savannas, plant diversity decreased with growing human pressures.

In Europe, major migrations over the Holocene are associated with increased biodiversity. The first migration around 9,000 years ago involved Neolithic farmers moving from the Fertile Crescent into Europe. The second, around 5,000 years ago, saw horse-riding pastoralists from the central Asian steppe, the Yamnaya, spread into Europe. These populations likely cleared forests for agriculture and settlements, creating a patchy landscape where diverse plant species could thrive.

Creating a patchy forest is easier than diversifying open grasslands, as it's simpler to clear trees and let open-ground plants colonize. This ease may explain historic differences in vegetation patterns worldwide.

Rewilding and Human Influence

Modern conservation efforts often advocate for rewilding, minimizing human influence to boost biodiversity. However, historical evidence suggests that human-modified landscapes can enhance biodiversity. Many of Europe’s biodiverse regions today are traditionally managed, low-intensity farmlands like Alpine meadows and the dehesas and montados in Spain and Portugal.

Removing human presence to improve ecosystem health and diversity might sometimes be counterproductive. Research indicates that biodiversity often flourishes due to centuries of human interaction with ecosystems. Recognizing the positive impacts of traditional land use can inform and improve contemporary conservation strategies.

Conclusion

The ancient farming practices of our ancestors offer a valuable blueprint for enhancing biodiversity today. While minimizing human impact is crucial in some contexts, incorporating traditional land management practices could foster more diverse and resilient ecosystems. By learning from the past, we can better navigate the challenges of conserving our planet’s biodiversity in the future.

1. Gordon, J. D., Fagan, B., Milner, N., & Thomas, C. D. (2024). Floristic diversity and its relationships with human land use varied regionally during the Holocene. Nature Ecology & Evolution, 1–13. https://doi.org/10.1038/s41559-024-02457-x