The phrase "a decrease in the richness of" is correct and usable in written English.
It can be used when discussing a reduction in the variety, quality, or abundance of something, often in contexts related to ecology, culture, or resources.
Example: "The study revealed a decrease in the richness of biodiversity in the affected areas due to pollution."
Alternatives: "a reduction in the diversity of" or "a decline in the abundance of".
However, the presence of herbicide was associated with a decrease in the species richness of recorded protist taxa and a predominance of robust, cosmopolitan or ubiquitous protist genera.
Within endophytes, a significant decrease in the richness of beneficial fungi was observed in symptomatic twigs.
Lack of that experience, however, led to a decrease of the richness of connection and size of those brain cells.
This is because an increase in patch richness (e.g. UK pastures rich in earthworms) may lead to a decrease in the mean number of patches per territory.
These can lead to a decrease in species richness and the abundance of individual species towards the centre of cities and towns.
Our findings also indicate that a drier future would likely have a large impact upon wetland plant communities with a decrease in species richness and an increase in the abundance of drought-tolerant emergent species.
Shahriary et al. (2012) also reported a decrease in species richness with increased grazing intensity around the piospheres of Iran.
A recent meta-analysis documented an increase in fish species richness with moderate declines in coral cover that shifted to a decrease in richness with more severe declines of coral [52], consistent with the model of intermediate disturbance.
While the annual variation amongst treatments was not significant, the results of this study suggest that fall burns support higher overall richness and native species richness; spring burns yield a decrease in overall richness, but an increase in native species richness; and summer burns contribute to an initial decline in overall and native species richness.
Deforestation led to a decrease in both functional richness and community-weighted specialization, particularly precluding the persistence of specialized species in disturbed forests.
