Meadows and climate change

Ecological consequencesedit

Climate changes impact temperature precipitation patterns worldwide. The effects are regionally very different but generally, temperatures tend to increase, snowpacks tend to melt earlier and many places tend to become drier. Many species respond to these changes by slowly moving their habitat upwards. The increased elevation decreases mean temperatures and thus allows for species to largely maintain their original habitat. Another common response to changed environmental conditions are phenological adaptations. These include shifts in the timing of germination or blossoming. Other examples include for example changing migration patterns of birds of passage. These adaptations are primarily influenced by three drivers:

• Increased temperature
• Changing precipitation patterns
• Reduced snowpack and earlier melting

Effects of higher temperaturesedit

In response to temperature changes, flowering plants can respond through either spatial or temporal shifts. Spatial shifts refers to the migration towards colder areas, often on higher altitudes. A temporal shift means that a plant may alter its phenology to blossom at a different time of the year. By moving towards the early spring or late autumn they can restore their previous temperature conditions. These adaptations are limited through. Spatial shifts may be difficult if the areas are already inhabited by other species, or when the plant is reliant on specific hydrology or soil type. Other authors have shown that higher temperatures can increase total biomass, but temperature shocks and instability seem to have negative impacts on biodiversity. This even appears to be the case for multiyear species, which were previously considered to have a buffering effect on extreme weather events.

Effects of changing precipitation patternsedit

There is a variety of hydrological regimes for meadows, ranging from dry to humid, each yielding different plant communities adapted to the respective provider of water. A shift in precipitation patterns has very different effects, depending on the type of meadow. Meadows that are either dry or wet appear to be rather resilient to change, as a moderate increase or decrease in precipitation does not radically alter their character. Meanwhile, mesic meadows, with a moderate supply of water do change their character as it is easier to tip them into a different regime. Dry meadows in particular are threatened by the invasion of shrubs and other woody plants and a decreasing prevalence of flowering forbs, whereas hydric sites tend to lose woody species. Due to the dryer upper soil layers, forbs with shallow roots have difficulties obtaining enough water. Woody plants in contrast with their lower-reaching root systems can still extract water stored in lower soil layers and are able to sustain themselves through longer drought periods with their stored water reserves. In the longer term, changing hydrologic regimes may also facilitate the establishment of invasive species that may be better adapted to the new conditions. The effects are already quite visible, an example is the substitution of Alpine meadows in the southern Himalayas through shrubland. Climate change appears to be an important driver of this process. Wetter winters in contrast might increase total biomass, but favour already competitive species. By harming specialised plants and promoting the prevalence of more generalist species, more unstable precipitation patterns could also reduce ecological biodiversity.

Effects of reduced snowpacksedit

Snow covers are directly related to changes in temperature, precipitation and cloud cover. Still, changes in the timing of the snowmelt seem to be, particularly in alpine regions, an important determinant for phenological responses. There is even data suggesting that the impact of snowmelt is even higher than the warming alone. Earlier are not uniformly positive for plants though, as moisture injected through snow-melt might be missing later in the year. Additionally, it might allow for longer periods of seed predation. Problematic is also the lack of the insulating snow cover, springtime frost events might have a larger negative impact.

Effects on ecological communitiesedit

All the drivers mentioned above give rise to complex, non-linear community responses. These responses can be disentangled by looking at multiple climate drivers and species together. As different species show varying degrees of phenological responses, the consequence is a so-called phenological reassembly, where the structure of the ecosystem changes fundamentally. Phenological responses in blossoming periods of certain plants may not coincide with the phenological shifts of their pollinators or growing periods of plant communities relying on each other may start to diverge. A study of meadows in the Rocky Mountains revealed the emergence of a mid-season period with little floral activity. Specifically, the study identified that the typical mid-summer floral peak was composed out of several consecutive peaks in dry, mesic and wet meadow systems. Phenological responses to climate change let these distinct peaks diverge, leading to a gap during mid-summer. This poses a threat to pollinators relying on a continuous supply of floral resources. As ecological communities are often highly adapted to local circumstances which can not be reproduced at higher elevations, Debinski et al. describe the short-term changes observed on meadows "as a shift in the mosaic of the landscape composition". Therefore, it is important to monitor not only how specific species respond to climate change, but to also investigate them in the context of different habitats they occur in.

Phenological Reassemblyedit

Animals as well as plants are changing rapidly to the anthropogenic global warming, and the number of individuals, habitat occupancy, changing reproductive cycles are the strategies to adapt to this sever and unpredictable environment alterations. The different types of meadows all around the planet are different communities of plants (perennial and annual plants) that constantly are interacting with each other to stay alive and reproduce. Timing and duration of flowering is one of the phenological reassembly driven by many different factors like snow melt, temperature and soil moisture to mention a few. All of the changes that a plant or an animal may go through are depending in habitat’s topography, altitude, and latitude of a specific organism. It is important to monitored properly the plants because they are one of the best bioindicators of how climate changes is affecting the planet.

Flowering phenology is one of the most important features of plant in order to survive any type of adversity. Thanks to different modern techniques and constant monitoring we can assure which ecological strategy the plants are using in order to multiply their specie. In alpine meadow of the eastern Tibet notorious variances and similarities were observed between annual and perennial plants. Where perennial plants flowering peak date was directly proportional to the duration and inversely proportional in annuals plants. This are just a limited quantity of many relationships on phenology and functional traits interacting with the environment to survive.

Extreme weatheredit

Climate change is increasing temperatures all over the world, and boreal regions are more susceptible to suffer noticeable changes. An experiment was conducted to monitor the reaction of alpine arctic meadow plants to different patterns of increased temperatures. This experiment was based on vascular plants that live in arctic and subarctic environments within three different levels of vegetation: canopy layer, bottom layer and functional groups. It is crucial to keep on mind that these plants are usually sharing the space and constantly interacting with bryophytes, lichens, arthropods, animals and many other organisms. The result was a clear adaptation of a constant pattern that plants recognized and had time to reach thermal acclimation meaning that they got a net carbon gain by intensifying photosynthesis and slightly increasing respiration thanks to a warmer climate for a reasonable time period. However plants that suffer changes of any kind ( not only temperature rising and falling) in a short period of time are more likely to die because they did not have enough time to reach thermal acclimation.

Meadow restorationsedit

Carbon storage in meadowsedit

Meadows can act as substantial sinks and sources of organic carbon, holding vast quantities of it in the soil. The fluxes of carbon depend mainly on the natural cycle of carbon uptake and efflux, which interplays with seasonal variations (e.g non-growing vs growing season). The wide range of meadow subtypes have in turn differing attributes (like plant configurations) affecting the area's ability to act as sinks; seagrass meadows are for instant identified as some of the more important sinks in the global carbon cycle. In the instance of seagrass meadows, enhanced production of other greenhouse gases (CH₄ and N₂O) does occur but the estimated overall effect results in an offset of the total emission. Meanwhile, a usual driver of meadow loss (except for direct alterations due to human development) is climate change, consequently increasing carbon emissions and bringing up the topic of restoration projects which in some cases have prompted initiated meadow restorations (e.g Zostera marina meadow in Virginia U.S.A).

Grassland degradationsedit

Where grassland degradation has occurred, significant alterations to the carbon dioxide efflux during the non-growing season may take place. Both climate change and overgrazing factor into the degradation. As exemplified by the alpine wetland meadow on the Qinghai-Tibetan Plateau, there is the potential of being a moderate source of CO₂ and a carbon sink, due to high soil organic content and low decomposition. The more the dynamics have been quantified, however, the effects of degradation become more tangible. A strong connection between grassland degradation and soil carbon loss has been seen, pinpointing that carbon dioxide release is being stimulated by this event. This subsequently indicates a climate change mitigation potential by restoring degraded grassland.

Cap-and-tradeedit

Being a market-based regulation of emissions, the cap-and-trade system can in some instances be found incorporating restoration projects for climate mitigation. For example, the cap-and-trade program in California is looking at how meadow restorations can be incorporated into their system of reducing carbon emissions. The preliminary studies are, as depicted by Audubon, pointing at the potential of storing a substantially increased amount of soil carbon compared to degraded meadows, while boosting the local biodiversity. Most recently though, during the COVID-19 pandemic, difficulties with restoration are beginning to show: During the first years, areas under restoration are vulnerable to outside disruption, like meadow management put on hold when the ecosystem is most sensitive, for example to invasive species.