The history of life on Earth is closely associated with environmental change on multiple spatial and temporal scales. Climate change is a long-term change in the average weather patterns that have come to define Earth’s local, regional and global climates. These changes have a broad range of observed effects that are synonymous with the term. Climate change is any significant long term change in the expected pattern, whether due to natural variability or as a result of human activity. Predicting the effects that climate change will have on plant biodiversity can be achieved using various models, however bioclimatic models are most commonly used.
Environmental conditions play a key role in defining the function and geographic distributions of plants, in combination with other factors, thereby modifying patterns of biodiversity. Changes in long term environmental conditions that can be collectively coined climate change are known to have had enormous impacts on current plant diversity patterns; further impacts are expected in the future. It is predicted that climate change will remain one of the major drivers of biodiversity patterns in the future. Climate change is thought to be one of several factors causing the currently ongoing human-triggered mass extinction, which is changing the distribution and abundance of many plants.
Palaeo context
The Earth has experienced a constantly changing climate in the time since plants first evolved. In comparison to the present day, this history has seen Earth as cooler, warmer, drier and wetter, and (carbon dioxide) concentrations have been both higher and lower. These changes have been reflected by constantly shifting vegetation, for example forest communities dominating most areas in interglacial periods, and herbaceous communities dominating during glacial periods. It has been shown through fossil records that past climatic change has been a major driver of the processes of speciation and extinction. The best known example of this is the Carboniferous Rainforest Collapse which occurred 350 million years ago. This event decimated amphibian populations and spurred on the evolution of reptiles.
Modern context
There is significant current interest and research focus on the phenomenon of recent anthropogenic climate changes, or global warming. Focus is on identifying the current impacts of climate change on biodiversity, and predicting these effects into the future.
Changing climatic variables relevant to the function and distribution of plants include increasing concentrations, increasing global temperatures, altered precipitation patterns, and changes in the pattern of 'extreme weather events such as cyclones, fires or storms. Highly variable species distribution has resulted from different models with variable bioclimatic changes.
Because individual plants and therefore species can only function physiologically, and successfully complete their life cycles under specific environmental conditions (ideally within a subset of these), changes to climate are likely to have significant impacts on plants from the level of the individual right through to the level of the ecosystem or biome.
Effects of
concentrations have been steadily rising for more than two centuries. Increases in atmospheric concentration affect how plants photosynthesise, resulting in increases in plant water use efficiency, enhanced photosynthetic capacity and increased growth. Increased CO2 has been implicated in 'vegetation thickening' which affects plant community structure and function. Depending on environment, there are differential responses to elevated atmospheric CO2 between major 'functional types' of plant, such as and plants, or more or less woody species; which has the potential among other things to alter competition between these groups. Increased CO2 can also lead to increased Carbon : Nitrogen ratios in the leaves of plants or in other aspects of leaf chemistry, possibly changing herbivore nutrition. Studies show that doubled concentrations of CO2 will show an increase in photosynthesis in C3 plants but not in C4 plants. However, it is also shown that plants are able to persist in drought better than the plants.