There is an ongoing decline in plant biodiversity, just like there is ongoing biodiversity loss for many other life forms. One of the causes for this decline is climate change. [1] [2] [3] 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. [4]
Extended fire weather seasons may result in more severe burn conditions and shorter burn intervals, which can threaten the biodiversity of native vegetation. [5] Besides, species habitat changes or migrations under changing weather conditions can cause non-native plants [6] and pests to impact native vegetation diversity, making the latter less structurally functional and more vulnerable to external damage, [7] leading to biodiversity loss.
Predicting the effects that climate change will have on plant biodiversity can be achieved using various models. Bioclimatic models are most commonly used. [8] [9]
Changing climatic variables relevant to the function and distribution of plants include increasing CO2 concentrations (see CO2 fertilization effect), increasing global temperatures, altered precipitation patterns, and changes in the pattern of 'extreme weather events such as cyclones, fires or storms.
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.
One common hypothesis among scientists is that the warmer an area is, the higher the plant diversity. This hypothesis can be observed in nature, where higher plant biodiversity is often located at certain latitudes (which often correlates with a specific climate/temperature). [10] Plant species in montane and snowy ecosystems are at greater risk for habitat loss due to climate change. [11] The effects of climate change are predicted to be more severe in mountains of northern latitude. [11]
If climatic factors such as temperature and precipitation change in a region beyond the tolerance of a species phenotypic plasticity, then distribution changes of the species may be inevitable. [12] There is already evidence that plant species are shifting their ranges in altitude and latitude as a response to changing regional climates. [13] [14] Yet it is difficult to predict how species ranges will change in response to climate and separate these changes from all the other man-made environmental changes such as eutrophication, acid rain and habitat destruction. [15] [16] [17]
When compared to the reported past migration rates of plant species, the rapid pace of current change has the potential to not only alter species distributions, but also render many species as unable to follow the climate to which they are adapted. [18] The environmental conditions required by some species, such as those in alpine regions may disappear altogether. The result of these changes is likely to be a rapid increase in extinction risk. [19] Adaptation to new conditions may also be of great importance in the response of plants. [20]
Predicting the extinction risk of plant species is not easy however. Estimations from particular periods of rapid climatic change in the past have shown relatively little species extinction in some regions, for example. [21] Knowledge of how species may adapt or persist in the face of rapid change is still relatively limited.
It is clear now that the loss of some species will be very dangerous for humans because they will stop providing services. Some of them have unique characteristics that cannot be replaced by any other. [22]
Distributions of species and plant species will narrow following the effects of climate change. [11] Climate change can affect areas such as wintering and breeding grounds to birds. Migratory birds use wintering and breeding grounds as a place to feed and recharge after migrating for long hours. If these areas are damaged due to climate change, it will eventually affect them as well. [23]
Lowland forest have gotten smaller during the last glacial period and those small areas became island which are made up of drought resisting plants. In those small refugee areas there are also a lot of shade dependent plants. [22] As an example, the dynamics of the calcareous grassland were significantly impacted due to the climate factors. [24]
Changes in the suitability of a habitat for a species drive distributional changes by not only changing the area that a species can physiologically tolerate, but how effectively it can compete with other plants within this area. Changes in community composition are therefore also an expected product of climate change.
The timing of phenological events such as flowering are often related to environmental variables such as temperature. Changing environments are therefore expected to lead to changes in life cycle events, and these have been recorded for many species of plants. [13] These changes have the potential to lead to the asynchrony between species, or to change competition between plants. Both the insect pollinators and plant populations will eventually become extinct due to the uneven and confusing connection that is caused by the change of climate. [25] Flowering times in British plants for example have changed, leading to annual plants flowering earlier than perennials, and insect pollinated plants flowering earlier than wind pollinated plants; with potential ecological consequences. [26] A recently published study has used data recorded by the writer and naturalist Henry David Thoreau to confirm effects of climate change on the phenology of some species in the area of Concord, Massachusetts. [27] Another life-cycle change is warmer winter which can be leads to summer rainfall or summer drought. [24]
Data from 2018 found that at 1.5 °C (2.7 °F), 2 °C (3.6 °F) and 3.2 °C (5.8 °F) of global warming, over half of climatically determined geographic range would be lost by 8%, 16%, and 44% of plant species. This corresponds to more than 20% likelihood of extinction over the next 10–100 years under the IUCN criteria. [28] [29]
The 2022 IPCC Sixth Assessment Report estimates that while at 2 °C (3.6 °F) of global warming, fewer than 3% of flowering plants would be at a very high risk of extinction, this increases to 10% at 3.2 °C (5.8 °F). [29]
A 2020 meta-analysis found that while 39% of vascular plant species were likely threatened with extinction, only 4.1% of this figure could be attributed to climate change, with land use change activities predominating. However, the researchers suggested that this may be more representative of the slower pace of research on effects of climate change on plants. For fungi, it estimated that 9.4% are threatened due to climate change, while 62% are threatened by other forms of habitat loss. [30]
Alpine and mountain plant species are known to be some of the most vulnerable to climate change. In 2010, a study looking at 2,632 species located in and around European mountain ranges found that depending on the climate scenario, 36–55% of alpine species, 31–51% of subalpine species and 19–46% of montane species would lose more than 80% of their suitable habitat by 2070–2100. [31] In 2012, it was estimated that for the 150 plant species in the European Alps, their range would, on average, decline by 44%-50% by the end of the century - moreover, lags in their shifts would mean that around 40% of their remaining range would soon become unsuitable as well, often leading to an extinction debt. [32] In 2022, it was found that those earlier studies simulated abrupt, "stepwise" climate shifts, while more realistic gradual warming would see a rebound in alpine plant diversity after mid-century under the "intermediate" and most intense global warming scenarios RCP4.5 and RCP8.5. However, for RCP8.5, that rebound would be deceptive, followed by the same collapse in biodiversity at the end of the century as simulated in the earlier papers. [33] This is because on average, every degree of warming reduces total species population growth by 7%, [34] and the rebound was driven by colonization of niches left behind by most vulnerable species like Androsace chamaejasme and Viola calcarata going extinct by mid-century or earlier. [33]
It's been estimated that by 2050, climate change alone could reduce species richness of trees in the Amazon Rainforest by 31–37%, while deforestation alone could be responsible for 19–36%, and the combined effect might reach 58%. The paper's worst-case scenario for both stressors had only 53% of the original rainforest area surviving as a continuous ecosystem by 2050, with the rest reduced to a severely fragmented block. [35] Another study estimated that the rainforest would lose 69% of its plant species under the warming of 4.5 °C (8.1 °F). [36]
Another estimate suggests that two prominent species of seagrasses in the Mediterranean Sea would be substantially affected under the worst-case greenhouse gas emission scenario, with Posidonia oceanica losing 75% of its habitat by 2050 and potentially becoming functionally extinct by 2100, while Cymodocea nodosa would lose ~46% of its habitat and then stabilize due to expansion into previously unsuitable areas. [37]All species are likely to be directly impacted by the changes in environmental conditions discussed above, and also indirectly through their interactions with other species. While direct impacts may be easier to predict and conceptualise, it is likely that indirect impacts are equally important in determining the response of plants to climate change. [38] [39] A species whose distribution changes as a direct result of climate change may invade the range of another species or be invaded, for example, introducing a new competitive relationship or altering other processes such as carbon sequestration. [40]
The range of a symbiotic fungi associated with plant roots (i.e., mycorrhizae) [41] may directly change as a result of altered climate, resulting in a change in the plant's distribution. [42]
Predicting the effects that climate change will have on plant biodiversity can be achieved using various models, however bioclimatic models are most commonly used. [8] [9]
Accurate predictions of the future impacts of climate change on plant diversity are critical to the development of conservation strategies. These predictions have come largely from bioinformatic strategies, involving modeling individual species, groups of species such as 'functional types', communities, ecosystems or biomes. They can also involve modeling species observed environmental niches, or observed physiological processes. The velocity of climate change can also be involved in modelling future impacts as well. [43]
Although useful, modeling has many limitations. Firstly, there is uncertainty about the future levels of greenhouse gas emissions driving climate change [44] and considerable uncertainty in modeling how this will affect other aspects of climate such as local rainfall or temperatures. For most species the importance of specific climatic variables in defining distribution (e.g. minimum rainfall or maximum temperature) is unknown. It is also difficult to know which aspects of a particular climatic variable are most biologically relevant, such as average vs. maximum or minimum temperatures. Ecological processes such as interactions between species and dispersal rates and distances are also inherently complex, further complicating predictions.
Improvement of models is an active area of research, with new models attempting to take factors such as life-history traits of species or processes such as migration into account when predicting distribution changes; though possible trade-offs between regional accuracy and generality are recognised. [45]
Climate change is also predicted to interact with other drivers of biodiversity change such as habitat destruction and fragmentation, or the introduction of foreign species. These threats may possibly act in synergy to increase extinction risk from that seen in periods of rapid climate change in the past. [46]
The Holocene extinction, or Anthropocene extinction, is the ongoing extinction event caused by humans during the Holocene epoch. These extinctions span numerous families of plants and animals, including mammals, birds, reptiles, amphibians, fish, and invertebrates, and affecting not just terrestrial species but also large sectors of marine life. With widespread degradation of biodiversity hotspots, such as coral reefs and rainforests, as well as other areas, the vast majority of these extinctions are thought to be undocumented, as the species are undiscovered at the time of their extinction, which goes unrecorded. The current rate of extinction of species is estimated at 100 to 1,000 times higher than natural background extinction rates and is increasing. During the past 100–200 years, biodiversity loss and species extinction have accelerated, to the point that most conservation biologists now believe that human activity has either produced a period of mass extinction, or is on the cusp of doing so. As such, after the "Big Five" mass extinctions, the Holocene extinction event has also been referred to as the sixth mass extinction or sixth extinction; given the recent recognition of the Capitanian mass extinction, the term seventh mass extinction has also been proposed for the Holocene extinction event.
Conservation biology is the study of the conservation of nature and of Earth's biodiversity with the aim of protecting species, their habitats, and ecosystems from excessive rates of extinction and the erosion of biotic interactions. It is an interdisciplinary subject drawing on natural and social sciences, and the practice of natural resource management.
An ecological or environmental crisis occurs when changes to the environment of a species or population destabilizes its continued survival. Some of the important causes include:
Habitat destruction occurs when a natural habitat is no longer able to support its native species. The organisms once living there have either moved to elsewhere or are dead, leading to a decrease in biodiversity and species numbers. Habitat destruction is in fact the leading cause of biodiversity loss and species extinction worldwide.
The Holarctic realm is a biogeographic realm that comprises the majority of habitats found throughout the continents in the Northern Hemisphere. It corresponds to the floristic Boreal Kingdom. It includes both the Nearctic zoogeographical region, and Alfred Wallace's Palearctic zoogeographical region.
In biology, a refugium is a location which supports an isolated or relict population of a once more widespread species. This isolation (allopatry) can be due to climatic changes, geography, or human activities such as deforestation and overhunting.
Species richness, or biodiversity, increases from the poles to the tropics for a wide variety of terrestrial and marine organisms, often referred to as the latitudinal diversity gradient. The latitudinal diversity gradient is one of the most widely recognized patterns in ecology. It has been observed to varying degrees in Earth's past. A parallel trend has been found with elevation, though this is less well-studied.
There are several plausible pathways that could lead to an increased extinction risk from climate change. Every plant and animal species has evolved to exist within a certain ecological niche. But climate change leads to changes of temperature and average weather patterns. These changes can push climatic conditions outside of the species' niche, and ultimately render it extinct. Normally, species faced with changing conditions can either adapt in place through microevolution or move to another habitat with suitable conditions. However, the speed of recent climate change is very fast. Due to this rapid change, for example cold-blooded animals may struggle to find a suitable habitat within 50 km of their current location at the end of this century.
Reserve design is the process of planning and creating a nature reserve in a way that effectively accomplishes the goal of the reserve.
The Future of Marine Animal Populations (FMAP) project was one of the core projects of the international Census of Marine Life (2000–2010). FMAP's mission was to describe and synthesize globally changing patterns of species abundance, distribution, and diversity, and to model the effects of fishing, climate change and other key variables on those patterns. This work was done across ocean realms and with an emphasis on understanding past changes and predicting future scenarios.
Forest migration is the movement of large seed plant dominated communities in geographical space over time.
In paleoecology and ecological forecasting, a no-analog community or climate is one that is compositionally different from a baseline for measurement. Alternative naming conventions to describe no-analog communities and climates may include novel, emerging, mosaic, disharmonious and intermingled.
The effects of climate change in Saskatchewan are now being observed in parts of the province. There is evidence of reduction of biomass in Saskatchewan's boreal forests that is linked by researchers to drought-related water stress stemming from global warming, most likely caused by greenhouse gas emissions. While studies, as early as 1988 have shown that climate change will affect agriculture, whether the effects can be mitigated through adaptations of cultivars, or crops, is less clear. Resiliency of ecosystems may decline with large changes in temperature. The provincial government has responded to the threat of climate change by introducing a plan to reduce carbon emissions, "The Saskatchewan Energy and Climate Change Plan", in June 2007.
Biodiversity loss happens when various species disappear completely from Earth (extinction) or when there is a decrease or disappearance of species in a specific area. This in turn leads to a reduction in biological diversity in that area. The decrease can be temporary or permanent. It is temporary if the damage that led to the loss is reversible in time, for example through ecological restoration. If this is not possible, the decrease is permanent. This ongoing global extinction is a biodiversity crisis. The cause of most of the biodiversity loss is human activity that pushes the planetary boundaries too far.
An ecosystem, short for ecological system, is defined as a collection of interacting organisms within a biophysical environment. Ecosystems are never static, and are continually subject to stabilizing and destabilizing processes alike. Stabilizing processes allow ecosystems to adequately respond to destabilizing changes, or pertubations, in ecological conditions, or to recover from degradation induced by them: yet, if destabilizing processes become strong enough or fast enough to cross a critical threshold within that ecosystem, often described as an ecological 'tipping point', then an ecosystem collapse occurs.
Climate change and invasive species refers to the process of the environmental destabilization caused by climate change. This environmental change facilitates the spread of invasive species — species that are not historically found in a certain region, and often bring about a negative impact to that region's native species. This complex relationship is notable because climate change and invasive species are also considered by the USDA to be two of the top four causes of global biodiversity loss.
Disease ecology is a sub-discipline of ecology concerned with the mechanisms, patterns, and effects of host-pathogen interactions, particularly those of infectious diseases. For example, it examines how parasites spread through and influence wildlife populations and communities. By studying the flow of diseases within the natural environment, scientists seek to better understand how changes within our environment can shape how pathogens, and other diseases, travel. Therefore, diseases ecology seeks to understand the links between ecological interactions and disease evolution. New emerging and re-emerging infectious diseases are increasing at unprecedented rates which can have lasting impacts on public health, ecosystem health, and biodiversity.
Significant work has gone into analyzing the effects of climate change on birds. Like other animal groups, birds are affected by anthropogenic (human-caused) climate change. The research includes tracking the changes in species' life cycles over decades in response to the changing world, evaluating the role of differing evolutionary pressures and even comparing museum specimens with modern birds to track changes in appearance and body structure. Predictions of range shifts caused by the direct and indirect impacts of climate change on bird species are amongst the most important, as they are crucial for informing animal conservation work, required to minimize extinction risk from climate change.
Climate change has already been altering biomes, adversely affecting terrestrial and marine ecosystems alike. Climate change represents the long-term alteration of temperature and average weather patterns, in addition to a substantial increase in both the frequency and intensity of extreme weather events. As the area's climate changes, a change in its flora and fauna follows. For instance, out of 4000 species analyzed by the IPCC Sixth Assessment Report, half were found to have shifted their distribution to higher latitudes or elevations in response to climate change.
Jens-Christian Svenning is a Danish ecologist, biogeographer and academic. He is a Professor at the Department of Biology at Aarhus University, Denmark where he also serves as the Director of DNRF Center for Ecological Dynamics in a Novel Biosphere (ECONOVO), established in 2023.
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