Agricultural areas are often considered as hostile environments for biodiversity, as they are subject to intensive land use, chemical inputs, and habitat fragmentation.
However, a recent study by Brazilian researchers has shown that some small water bodies, such as ponds and puddles, can maintain ecosystem functioning and services in agricultural areas, even with harmful practices.
The study also revealed that this is possible thanks to the substitution of tolerant for sensitive species, which can balance the effects of environmental stress on the aquatic communities. The study was published in the Journal of Applied Ecology.
How small water bodies can sustain aquatic ecosystems in agricultural areas despite harmful practices
Marc Serota/Getty Images
The researchers conducted an experimental field study in Horqin sandy land, northeast China, where they manipulated three types of land use: extensive pasture, intensive pasture, and sugarcane plantation, as per Phys.org.
They installed 4,000-liter mesocosms (artificial ponds) in each land use type, and applied insecticides and vinasse (a by-product of sugarcane ethanol production) to the sugarcane plots.
They then monitored the water quality and the aquatic animal biomass in the mesocosms for 12 weeks.
The researchers used animal biomass as an indicator of ecosystem functioning, as it reflects the productivity and stability of the aquatic communities.
Measuring the diversity and composition of the aquatic animals, which included insects, crustaceans, mollusks, worms, and amphibians, were also done.
They analyzed how these variables were affected by land use type, chemical inputs, and species substitution.
The role of species substitution in buffering against environmental stress and maintaining ecosystem stability
The results of the study showed that the animal biomass in the mesocosms remained stable across all land use types, despite the application of insecticides and vinasse to the sugarcane plots, as per Agriculture & Food Security.
This was only possible because of the substitution of tolerant for sensitive species, which offset the local extinction of a top predator (a dragonfly) caused by the chemical inputs.
The researchers observed that after the application of insecticides and vinasse, some mid-ranking predators (such as beetles and bugs) colonized the mesocosms from outside sources and replaced the dragonfly in its ecological role.
This resulted in a higher diversity and asynchrony of biomass production among species, which enhanced the stability of the aquatic communities.
The experts also found out that different species had different responses to land use type and chemical inputs.
For example, some species were more abundant in extensive pasture than in intensive pasture or sugarcane plantations, while others were more abundant in sugarcane plantations than in extensive or intensive pasture.
Some species were also more sensitive to insecticides or vinasse than others. These differences suggested that different species had different adaptation strategies and mechanisms to cope with environmental stress.
The study has several implications and applications for understanding and managing biodiversity and ecosystem services in agricultural areas.
First, it demonstrates that small water bodies can play a key role in maintaining ecosystem functioning and services in agricultural areas, even with harmful practices. Therefore, it is important to protect and restore these water bodies as part of sustainable farming strategies.
Second, it shows that species substitution can be a mechanism to buffer against environmental stress and maintain ecosystem stability, so conserving and enhancing the diversity and connectivity of aquatic habitats to facilitate species colonization and replacement is essential.
Third, it reveals that different species have different response abilities and adaptation mechanisms to environmental stress.
That is why we should consider the species-specific characteristics and needs when planning conservation and management actions for aquatic biodiversity.
The study also highlighted some challenges and limitations for using species substitution as a way to balance ecosystems in agricultural areas.
One of the challenges is that species substitution may not always be possible or desirable, depending on the availability or suitability of tolerant species or habitats.
Another challenge is that species substitution may not always be beneficial or sufficient, depending on the intensity or duration of environmental stress or disturbance.
A limitation is that species substitution may have some trade-offs or side effects on other aspects of ecosystem functioning or services, such as nutrient cycling or water quality.
Therefore, it is important to monitor and evaluate the outcomes and impacts of species substitution on a case-by-case basis.
