Changes in land use, particularly deforestation and urbanisation, significantly impact the carbon cycle. Deforestation, the removal of large areas of forests, directly affects the carbon cycle by reducing the number of trees that can absorb CO₂ from the atmosphere through photosynthesis. This not only increases the amount of CO₂ in the atmosphere but also means that less carbon is stored in trees and soil. When forests are replaced with agricultural land or urban areas, the carbon storage capacity of these areas is greatly reduced. Urbanisation contributes to the carbon cycle disruption by increasing the demand for fossil fuels, leading to higher CO₂ emissions. Furthermore, the construction and maintenance of urban infrastructure result in significant carbon emissions. These changes in land use contribute to an imbalance in the carbon cycle, exacerbating global warming and climate change.

The burning of fossil fuels disrupts the carbon cycle in a more profound way compared to natural processes like wildfires. Fossil fuels, such as coal, oil, and natural gas, are essentially carbon that has been stored underground for millions of years. When these fuels are burnt, they release this stored carbon into the atmosphere as carbon dioxide, significantly increasing the atmospheric concentration of this greenhouse gas. Unlike wildfires, which are part of the natural carbon cycle and typically result in the release of carbon that is quickly reabsorbed by plant regrowth, the carbon released from fossil fuels does not have an immediate natural pathway for reabsorption. This leads to an accumulation of carbon dioxide in the atmosphere, contributing to the greenhouse effect and climate change. In contrast, wildfires, although they can be severe and destructive, generally have a temporary impact on the carbon cycle, with ecosystems usually recovering and resequestering the carbon over time.

Oceans play a crucial role in regulating the carbon cycle. They absorb about a quarter of the carbon dioxide emitted into the atmosphere by human activities, making them a major carbon sink. This absorption is a critical process in moderating global climate change. However, increased levels of atmospheric CO₂ affect oceans in two significant ways. Firstly, as oceans absorb more CO₂, they become more acidic. Ocean acidification can have detrimental effects on marine life, particularly organisms with calcium carbonate shells or skeletons, such as corals and some plankton species. These organisms are crucial for the marine food web and their decline can have cascading effects on the entire marine ecosystem. Secondly, warmer global temperatures, a result of increased greenhouse gases, lead to ocean warming. Warmer oceans absorb less CO₂ and can lead to the release of previously stored carbon, further exacerbating global warming. These changes not only disrupt the carbon cycle but also threaten the health and diversity of marine ecosystems.

Human-engineered processes, often referred to as carbon capture and storage (CCS) technologies, aim to mitigate carbon dioxide levels in the atmosphere by mimicking natural carbon sinks. These technologies involve capturing CO₂ emissions from sources like power plants and industrial processes, transporting it to a storage site, and depositing it where it will not enter the atmosphere, often in deep geological formations. While CCS technologies are promising, they are still in developmental stages and face several challenges. These include high costs, energy requirements, and concerns about the long-term stability and safety of CO₂ storage sites. Moreover, these technologies do not address the root causes of high CO₂ emissions, such as fossil fuel dependence. Therefore, while CCS can be part of the solution, it is not a substitute for reducing emissions through sustainable practices like renewable energy usage, energy efficiency improvements, and behavioural changes.

The increase in atmospheric carbon dioxide, primarily due to human activities such as burning fossil fuels and deforestation, has a significant impact on the carbon cycle. The excess carbon dioxide enhances the greenhouse effect, leading to global warming and climate change. This disturbs the delicate balance of the carbon cycle. For instance, higher levels of CO₂ in the atmosphere can accelerate plant growth (a phenomenon known as CO₂ fertilisation), altering the rate of photosynthesis and potentially impacting the food chain and biodiversity. Additionally, increased CO₂ levels in the atmosphere lead to ocean acidification. As oceans absorb more CO₂, it reacts with seawater to form carbonic acid, which lowers the pH of the water, affecting marine life and coral reefs. These changes can disrupt the entire carbon cycle, affecting not just the climate but also the health of various ecosystems on which life depends.