Human activity that has contributed to the conversion of grasslands into farmland is agriculture.

Agriculture is the practice of cultivating plants and raising animals for food, fiber, and other products used to sustain human life. It involves the clearing and tilling of land to prepare it for planting crops or grazing livestock.

Here are the reasons why agriculture has led to the conversion of grasslands into farmland:

1. Clearing of land: To create farmland, grasslands are often cleared of their natural vegetation, including grasses and shrubs. This process involves the removal of plants through methods such as cutting, burning, or using heavy machinery to clear the land. Clearing the grasslands allows for the planting of crops or the establishment of pastures for livestock.

2. Tilling the soil: Once the land is cleared, farmers use various techniques to prepare the soil for planting. Tilling involves breaking up the soil, removing weeds, and creating a favorable environment for seed germination and plant growth. This process disrupts the natural grassland ecosystem and replaces it with agricultural crops.

3. Irrigation: In many cases, grasslands are converted into farmland in areas where water availability is limited. To grow crops, farmers often need to implement irrigation systems to provide water to the plants. This involves diverting water from nearby sources such as rivers or underground aquifers, which can further alter the natural water flow patterns in grassland ecosystems.

4. Use of fertilizers and pesticides: Agricultural practices often involve the use of fertilizers and pesticides to enhance crop growth and protect them from pests and diseases. However, excessive use of these chemicals can lead to environmental issues such as water pollution and soil degradation, further impacting the grassland ecosystem.

5. Intensive farming practices: Modern agriculture often relies on intensive farming practices to maximize crop yields. This includes the use of machinery, synthetic fertilizers, and genetically modified crops. These practices can have significant impacts on grasslands, including soil erosion, loss of biodiversity, and habitat destruction.

In conclusion, agriculture has played a major role in the conversion of grasslands into farmland. The clearing of land, tilling of soil, irrigation, use of fertilizers and pesticides, and intensive farming practices have all contributed to the transformation of grassland ecosystems into agricultural landscapes.