The invasive plants have had several negative impacts on native island plant species, including the competitive exclusion of many such species. The out-competition will and can alter the structure of plant communities and the quality of the islands' soil. Introduced vegetation has altered long-term carbon storage as well as the reduction of CO2 in the atmosphere. Native plants such as fern bushes, "Phylica" bushes, fern brakes, mires, and bogs, contain high organic content matter which functions as storage for carbon. With the introduction of harmful species, the islands will see a decrease in carbon storage of both the soil and vegetation. With multiple changes occurring within the soil due to invasive plant species, the nutrient cycle is bound to be negatively influenced. Invasive plants are also affecting the human population of Tristan da Cunha by being disease carriers and becoming agricultural pests in gardens and pastures.