How a 170-Year-Old Field Revolutionized Ecology
A quiet field in England holds secrets that have transformed our understanding of the natural world.
Imagine a scientific experiment that began before the American Civil War, outlasted two World Wars, and continues to yield groundbreaking discoveries to this day. The Park Grass Experiment, nestled at Rothamsted Research in Hertfordshire, England, is precisely that—the oldest ecological experiment in the world, initiated in 1856 and still actively studied7 . What started as a simple agricultural trial has blossomed into a cornerstone of modern ecology, revealing profound truths about biodiversity, evolution, and the delicate balance of our natural world.
The Park Grass Experiment has been running continuously for over 170 years, making it the world's oldest ecological field experiment.
In the mid-19th century, scientists John Bennet Lawes and Joseph Henry Gilbert sought to answer a practical question: how do different fertilizers and manures affect hay yields?3 5 . They established the Park Grass Experiment on approximately 2.8 hectares (6.9 acres) of land that had been permanent pasture for at least a century5 . The goal was straightforward—to help farmers improve their harvests.
What happened next, however, was unexpected. Within just two to three years of applying different treatments, the researchers noticed something extraordinary. The once-uniform field began to transform into a colorful tapestry of distinct plots, each with its own unique combination of grasses and flowers5 . The fertilizers were not just affecting yield; they were fundamentally changing the botanical makeup of the field. This accidental discovery marked the birth of a new scientific legacy, one that would eventually make Park Grass a legendary site for studying natural selection and biodiversity.
Lawes and Gilbert divided the field into plots, each receiving different nutrient applications5 . The treatments included:
These plots were further subdivided with variations in phosphorus, potassium, sodium, and magnesium applications5 . This comprehensive design allowed the scientists to observe not just the effects of fertilization, but how different nutrients interacted with each other.
As the experiment continued through the decades, its design was refined. A regular liming scheme was introduced in 1903 to study how correcting soil acidity affected the plant communities5 . The researchers also preserved physical samples of crops and soils, creating an invaluable historical archive that future scientists would use to track atmospheric pollution and even nuclear fallout.
The methodology for assessing results has also evolved. Initially, the focus was on hay yield measurements. Over time, however, scientists began conducting detailed botanical surveys, meticulously recording the percentage contribution of each species to the hay5 . This rich dataset, spanning more than a century and a half, has allowed ecologists to track changes in plant communities with unprecedented precision.
Field divided into multiple plots with different treatments
Different fertilizers applied at varying rates
Continuous data collection for over 170 years
Preservation of soil and plant samples for future analysis
The Park Grass Experiment has yielded insights far beyond its original agricultural purpose, fundamentally shaping our understanding of ecology.
One of the most striking findings is the powerful relationship between soil pH and plant diversity7 . The unfertilized plots maintained their original diversity of about 50 species, while the fertilized plots saw dramatic changes.
Applications of ammonium salts particularly acidified the soil, dramatically reducing species richness to just 2-3 plant types in the most extreme cases5 . This demonstrated that conventional field trials likely underestimate threats to plant biodiversity from long-term changes like soil acidification.
Park Grass has provided one of the first demonstrations of local evolutionary change under different selection pressures7 . Plant populations on different plots have become genetically distinct from one another.
For instance, researchers discovered inverse clines in flowering time in the grass Anthoxanthum odoratum across plot boundaries7 . This suggests that reproductive isolation between plots has been reinforced by natural selection—a potential case of evolution in action happening just meters apart.
The experiment has revealed how plant competition can amplify the effects of climate variation. During climatic perturbations like droughts, the intense competition for resources between plant species on the fertilized plots made these communities more vulnerable to change than the more diverse, unfertilized plots.
This finding has crucial implications for understanding how natural ecosystems might respond to climate change, suggesting that biodiversity provides resilience against environmental fluctuations.
| Treatment Type | Effect on Soil pH | Impact on Species Richness | Dominant Plant Groups |
|---|---|---|---|
| Unfertilized | Stable (~5.5) | High (35-45 species) | Mixed grasses and herbs |
| Ammonium Salts | Strong acidification | Low (2-3 species) | Grasses dominant |
| Organic Manures | Moderate change | Medium | Legumes and grasses |
| With Regular Liming | Corrected acidity | Higher than unlimed equivalents | More diverse herbs |
Fertilizers dramatically alter botanical composition - Founded basis for ecological succession studies
Liming effects on acidified soils - Revealed importance of pH management in agriculture
Local evolutionary changes in plants - Provided evidence for rapid evolution in real-time
Biodiversity recovery with reduced nitrogen pollution - Offered insights for ecosystem restoration
Today, Park Grass is both an Environmental Change Network site and an Ecological Continuity Trust site, recognizing its immense value for long-term environmental monitoring5 .
Researchers have incorporated advanced techniques including metagenomic analysis of soil microbes and molecular genetic markers applied to archived plant material5 7 . These technological advances have opened up entirely new avenues of investigation, allowing scientists to explore the genetic dynamics of plant populations over timescales no contemporary experiment could match.
A significant discovery emerged in 2015 when research revealed that grassland diversity on Park Grass showed signs of recovery once atmospheric nitrogen pollution reduced5 .
This finding offers hope that with proper pollution control, damaged ecosystems may possess a natural capacity for regeneration—a crucial insight for conservation efforts worldwide. It demonstrates that even long-term ecological damage might be reversible under the right conditions.
Preserves historical samples for future analysis. Enabled tracking of atmospheric pollution and nuclear fallout.
Modifies soil pH to study acidification effects. Demonstrated critical role of pH in maintaining biodiversity.
Documents species composition and abundance. Provided century-scale data on plant community dynamics.
Studies soil microbial communities. Modern technique revealing hidden dimensions of ecosystem.
Maintains treatment integrity over decades. Ensures scientific continuity across generations of researchers.
The Park Grass Experiment exemplifies how long-term studies grow in value with time, enabling scientists to investigate questions that were inconceivable at their inception7 . As Professor Jonathan Silvertown and colleagues noted in their comprehensive review, the experiment "has inspired new ecological theory and has helped ecologists to recognise the value of long-term experiments in ecological studies".
"The Park Grass Experiment has inspired new ecological theory and has helped ecologists to recognise the value of long-term experiments in ecological studies." - Professor Jonathan Silvertown
Perhaps most remarkably, the experiment continues to address contemporary environmental concerns. Its findings on soil acidification inform current agricultural practices, while its insights into biodiversity patterns guide conservation efforts. The documented evolutionary changes provide crucial evidence for understanding how species adapt to changing environments.
Beyond its scientific contributions, Park Grass stands as a powerful testament to the value of patience in science. In an era of rapid results and short-term projects, this centuries-old experiment reminds us that some of nature's deepest secrets reveal themselves not in years, but in generations. As climate change and biodiversity loss accelerate, the long-term perspective provided by this living laboratory may prove more valuable than ever—offering insights from the past to guide our future.
For more information on this remarkable experiment, the full dataset is available to researchers by request through Rothamsted Research's e-RA database5 .