This new study suggests that the origin of new forms of life requires millions or thousands of years. A warmer Earth might therefore promote biodiversity over the long term. However, it does not offer much comfort in the face of climate change. The vast majority of research examining current ecosystems suggests that a warmer Earth will ultimately lead to a loss of biodiversity around the world. However, diversity may increase locally, at least in some places.
Barriers encourage diversity
Although climate change is a leading cause of local extinctions, barriers to dispersal are also factors in the decline of species richness. These barriers may include dispersal mode and non-climatic niche requirements, which might be reduced under conditions of rapid environmental change. In contrast, the functional diversity of plant communities in modern European forests is the highest in locations where the estimated velocity of past climate change was the lowest.
The geographical location of species distributions affects local and regional diversity. Species diversity is highest in warm climates and topographically diverse areas such as the tropics, Himalayas, Indo-West Pacific, and the Caribbean. In a study of the tropics, Janzen noted that the higher elevation means a greater barrier to dispersal. This could explain the relatively high level of diversity in tropical forests.
The temperature-dependent ecological interactions and coevolutionary processes that determine alpha diversity are related to the distribution of species and the distance between them. These biotic limiting factors may restrict the range of a species and limit its capacity to disperse and invade. These limiting factors can explain the observed patterns of beta diversity. In tropical environments, however, species richness should not decline, despite the presence of warm climates near its location.
The extent of regional diversity in tropical areas is also related to the distribution of resources in the region. The distribution of pelagic marine organisms varies by temperature and latitude, with species richness increasing as tropical species expand towards the poles. The seasonality and water balance of the climate are also factors that limit species diversity in temperate waters. The latter has more barriers than warm climates, but this does not mean that they don’t exist at all.
Invasive species occupy territory without barriers
Invasive species are often associated with increased biodiversity in warm climates, where abiotic factors like temperature and moisture are more favorable to their survival. Invasive species, such as weeds, often exhibit traits and behavioral shifts in a new environment. These traits include the tendency to become larger than native populations. Blossey and Notzold compared plants from different habitats and found that European plants grew larger in the new environment than in their native land. This difference in size is attributed to natural selection. Other species may evolve defensive traits that allow them to fend off herbivore attacks.
The rate of introduction and spread of nonnative species can influence their invasive potential. Invasive species may initially stay in low numbers for years before exploding at a later date. This phenomenon is known as a lag effect. For example, Bromus tectorum, introduced to western North America in 1890, remained localized for 20 years before expanding. By 1930, it was dominating more than 200,000 km2 of the continent.
Increasing diversity in warm climates is a key factor for ensuring that we preserve the uniqueness of native species. Wetter climates are more likely to support invasive species because they are more apt to spread in a warmer region. Invasive species also tend to occupy a greater area when their competitors are weaker and less abundant. These results are encouraging for the management of invasive species because they will reduce the competition for native species. However, this does not mean that range change is beneficial to native species.
The impact of invasive species on native species is often difficult to assess. Invasive species may continue to expand and invade their new territory, while smaller populations may be overwhelmed. Invasive species may even threaten the survival of larger populations. Among invasive species, Spartina alterniflora invades San Francisco Bay, where it hybridizes with native Spartina foliosa. Its increased pollen output and male fitness have caused it to overgrow in the Bay and threaten the native species.
Global warming affects species distribution
A recent meta-analysis of climate change studies has found that the geographic ranges of terrestrial organisms are shifting at rates of 11.0 meters and 16.9 kilometers per decade. This is about two to three times faster than previously believed. These changes were greatest in regions that experience the most warming, and the average latitudinal shifts were large enough to track temperature change. This study, however, does not prove that climate change is directly responsible for species distribution shifts.
Rapid climate change will have a greater effect on species that have small ranges and limited climatic envelopes. For example, 25% of the Australian eucalyptus’ distributions are within an area of low annual temperature variation. In such a case, even a small increase in average temperature can shift the climatic envelope of a species, so that it no longer lives in its natural range. In fact, modelling suggests that by the year 2070, most species will experience novel climatic conditions.
In southern China, the potential habitat for D. involucrata would decrease by over 50 % under a rapid warming scenario. Although the remaining area would remain within its present range, its distribution would shift to the west. This shift is even more evident if uncertainties regarding future climate change are not factored in. While these changes may not completely wipe out the tigerwood species, they will likely reduce its population.
However, species distribution models do account for uncertainty in climate change. They predict the future distribution of climatically suitable habitats based on past and current data. This allows scientists to estimate how likely a species would be in a given location in 2070 if it is subject to climate change. Other species, such as endangered Tertiary relict trees like Davidia involucrata Baill, have a limited distribution in their current range.
In the North Atlantic, the climate is changing the distribution of some fish species. In the Mid-Atlantic, Atlantic mackerel and butterfish have been shifted further north and into deeper water because of warming waters. Additionally, changes in water temperature have affected their migration and reproduction patterns. Changing temperatures affect the ecosystem as a whole and have the potential to affect prey and human pressures. To fully understand how climate change is affecting species distribution, long-term monitoring programs are necessary.
Challenges of identifying factors that determine how quickly and thoroughly ecosystems recover from extreme climate events
Understanding the impacts of extreme climate events is crucial to protecting human societies and ecosystems. Extreme weather events are out of proportion and highly unpredictable. Yet they are rarely considered in numerical climate models. In addition, causal explanations of links between large-scale climatic circulation patterns and local occurrence of extreme climate events are rare. Finally, there is no comprehensive database of such events.
Changing climate patterns increase the frequency and amplitude of extreme events, and these extreme events threaten ecosystems more than average conditions or global trends. Moreover, they pose far-reaching impacts on societies in the 21st century. This paper discusses the reasons for the increased frequency and amplitude of extreme weather events, summarizes recent findings regarding meteorological extremes, and identifies gaps in ecological climate research.
Recent research shows that the Amundsen Sea in West Antarctica may already be at or near the tipping point. Meanwhile, deforestation in the Amazon rainforest and the Great Barrier Reef in Australia are also at risk of tipping points. Clearly, more research is needed to understand these changes, as well as possible cascading effects. However, now is the time to act before the Earth reaches a point of no return.
In the future, it is important to determine the role of climate change in the oceans’ water cycle. The water cycle and precipitation patterns will be influenced by global warming and regional warming, which is likely to increase the frequency and intensity of drought. The increase in drought and heatwaves is already threatening ecological resilience in parts of Africa, and the region’s climate is expected to be warm enough to bring more heat and drought. In addition, water shortages can trigger migration processes, which can spark latent ethnic conflicts and aggressive conflict. As refugees flee war-torn regions, many may be left without water.
