Vocabulary:

• Reclamation: returning a piece of damaged or unused land to a more productive state. Notably, reclamation refers to measures taken to alleviate problems, even if it creates an ecosystem different from the original.
• Reintroduction: the deliberate release or translocation of a locally extinct / extirpated species, to parts of its original / natural range
• Restoration: returning a habitat, environment, or ecosystem to its original condition or membership, prior to a disturbance (often anthropogenic)
• Rewilding: conservation effort focused on restoring sustainable biodiversity and ecosystem health by connecting and preserving wild areas (that have not been significantly modified by human activity or used for agriculture), and protecting or reintroducing keystone species/apex predators.

Outline of Notes:

• General rules of context:
  • Diversity hotspots in hills and low mountains, resulting from speciation associated with different altitudes
  • Rock type/geologic history and landcover
  • Latitude and longitude affect patterns
• Different goals of restoration and reclamation:
  • Reclamation: prioritize increasing ecosystem functioning, not structure
  • Restoration: return ecosystem to its original state as much as possible

→ Ideal, but usually not realistic

• Rewilding: conservation effort focused on restoring sustainable biodiversity and ecosystem health by connecting and preserving wild areas, and protecting or reintroducing keystone species/apex predators.
  • Goals:
    • Slow/prevent extinctions
    • Restore ecosystem health
    • Minimize dependence on human intervention and management
      • Let nature take care of itself to restore damaged ecosystems

What Does the Future Look Like?

• Anthropogenic influences shape ecology
• Some species will thrive due to these anthropogenic influences
• These species share common characteristics

Blog-style Summary:

Global ecology encompasses the interactions of Earth’s ecosystems with the geosphere, hydrosphere, and atmosphere.

Global wind and water currents combine with global temperatures to drive the five major climate zones: tropical, dry / arid, temperate, continental, and polar. The relationship between temperature and moisture drives global patterns in terrestrial biomes through net primary productivity (NPP). Where the climate varies, elevation, geology and soil type can shift the balance between different biome types. Biomes, in turn, select for different traits, contributing to global biodiversity.

Global Grand Challenges

Global challenges include events and processes that threaten large populations and many species across multiple continents. Global challenges often transcend national borders and require international cooperation for effective mitigation. Global challenges also increasingly impact global ecology.

Wildfires – predicting risk in a changing world

Wildfires pose a dual-threat to global ecology through habitat destruction and air pollution. Nearly 50% of ecoregions worldwide are characterized as having “very high” or “high” ecological vulnerability to fire (Figure 3), calculated based on post-fire regeneration delay and ecological indicators outlined in Table 1.

Wildfires require ignitions, continuous fuels, drought, and appropriate weather conditions. Ignitions increase the probability of a fire starting in the first place. Fuel continuity across the landscape increases the probability that a fire will spread, and drought increases the flammability of available fuels. Strong wind, high temperature, and low humidity contribute to “fire weather”, which collectively increases the probability of ignition, spread, and vegetation flammability. Climate change and increasing human populations drive changes in fuel loads associated with habitat fragmentation and fire exclusion – all of which further affects the main fire drivers.

In 2009, Krawchuck et al. modeled the observed global distribution of fires under current conditions (Figure 5). Then they predicted areas where fire would invade or retreat by 2039, if greenhouse gas emissions are emitted at mid-to-high levels (similar to climate models, but applied to estimate risk of wildfire). Keep in mind that fire invasion is caused by increased drought, ignitions, and fuel continuity (discussed in Figure 4, above). This means that fire is predicted to retreat in all the blue areas on Figure 6 (below) because habitat destruction and biodiversity loss will reduce the amount of available fuels.

In 2022, Harrison et al. predicted that tropical savanna and tropical deciduous broadleaf forest and woodland would be most affected by wildfires (Figure 7). Remember that trees and other vegetation contribute to Net Primary Productivity, meaning that wildfires will drive negative bottom-up control, with subsequent trophic cascades up the food webs in these habitats. In addition to decreasing energy resources (i.e., NPP), wildfires also reduce vertical structure (e.g., niche complexity), further reducing biodiversity.

Habitat destruction

Habitat destruction will alter the landscape ecology, increase disturbance, and affect the spread of active wildfires. Urbanization will keep wildfires from spreading because of increased habitat fragmentation. Additionally, the decrease in biodiversity will decrease the available fuel for wildfires in the long run. However, increased urbanization also means increased human activity which increases both the chances of starting wildfires and the severity of them through means such as climate change. As habitat destruction increases, both generalists and disturbance-tolerant species will be more likely to survive. In the long run, specialists may be able to thrive once prior specialist species have decreased and new environmental niches arise.

The gene pool and overall population sizes will decrease, leading to a lack of genetic diversity within metapopulations. The bottleneck effect and genetic drift may become more prominent. The connectivity between metapopulations will decrease, with fewer links between source and sink populations. The habitat structure will favor more edge species. With decreased biodiversity and connectivity, food sources will be more scarce and competition between species will increase. Dense populations with smaller ranges might expose them to new pathogens and increase disease transmission.

Food webs will be composed of more R-selected species with more offspring and faster generation times. Also, there will be a decreased amount of trophic levels, creating a “simpler” food chain. An increase for trophic level cascades can lead to more vulnerable populations, making keystone and indicator species more vital to conserve. Net primary productivity over terrestrial environments will decrease from deforestation and degradation of soils, which may cause a bottom-up chain reaction throughout the food chain.

Restoration may be an unfeasible approach since the “original state” might be an arbitrary point in time, since alterations of the community are constantly evolving to global or community trends. Reintroduction of locally extinct or extirpated species may have both positive and unintended consequences to the current food web, meaning the feasibility is dependent on which species is being introduced or the complexity of the community food web. Rewilding may be sustainable since it is less about alteration and more about connectivity between “undisturbed” areas, though issues can occur when there is a lack of such undisturbed/ unmodified landscapes. Reclamation may increase sustainability of an ecosystem’s functions/services but the alleviation of current problems might uproot or decrease the population of certain species that won’t thrive within this possibly different ecosystem. Future research should focus on allowing current destroyed or disturbed areas to lay “fallow” and see what direction nature is growing back, to determine which species should be introduced. Conservation efforts can also remove invasive species and help the environment to continue to support succession.

Invasive species

Invasive species have implications for ecosystems all around the world. They are components or interact with all kinds of topics and concepts that we have discussed in AEC 400 this semester. The most prevalent is pertaining to competition and population dynamics. Invasive species disrupt food webs and ecosystems by out-competing, or using up resources that other species may need in order to survive, reproduce, or thrive. They may compete with other species through resource consumption like food, space, or even sunlight for autotrophs. They fill in the space, or niche, that a native species would usually take up because they tend to fill the role that the native species would have faster because of their growth rate, dispersal, etc., as further explained below.

Invasive species often grow at an exponential rate. Typically as generalists, they can source a high food availability and cover. Not all invasive species are generalists, but the ones that cause harm to native ones typically are. There is a difference between non-native and invasive species, as non-native just means it’s not native, but invasive species are those that ARE often generalists and able to outcompete others. Often combined with a lack of natural predators and high reproductive rates, they can grow their population size and dispersal range very quickly.

Overall, invasive species can disrupt and modify ecosystem dynamics, landscape ecology, urban habitats, population dynamics and growth, competition, and so much more. Invasive species are harmful and they are absolutely everywhere. It’s important to have understanding and awareness about their impacts and implications on any type of issue or consideration when managing or learning about ecological interactions or occurrences.

Opportunistic feeders, invasive species, and species that are adapted to disturbed environments tend to thrive compared to other species when it comes to being affected by anthropogenic pressures. Generalists consume eat a variety of food sources and can find shelter in a multitude of different environments. As such, they may be better able to utilize food sources and shelter produced by humans. R-strategists with short gestation and high reproductive rates will adapt more quickly to changing conditions imposed by humans.

Restoration, Reintroduction, and Rewilding imply more human action to managing ecosystems. This is less feasible sometimes as opposed to letting natural systems attempt to take over because it requires planning, money, time, and monitoring based on success of the project. These two approaches are designed with long-term success and sustainability in mind which is better for future generations. Sometimes rewilding may just be letting the environment take over, or it could mean deliberate capture, breeding, and re-release of endangered species, often keystone species, to begin the process (like the gray wolves in Yellowstone), and then letting wildlife and plant life truly take over. Reclamation is beneficial but still less monumental than the other approaches since it involves just designating something or somewhere to an environmental cause, it’s more of a first step rather than a final solution like restoration or rewilding.

In the wake of devastating hurricanes, floods, and wildfires, researchers have a chance to study how ecosystems recover from these events. This is particularly relevant given the frequency at which these disasters are now occurring. Future research may benefit from focusing on how invasive species react to these massive disturbances. Given the nature of most invasive species (resilient, r-selective, etc.), disturbances may provide opportunity to gain leverage in an affected ecosystem. By conducting ecological surveys of affected ecosystems we can use concepts like population dynamics, succession, and food chain structure to interpret and utilize the data to make informed solutions for addressing and managing invasive species.

Population declines

Population declines have significant impacts on ecological processes and relationships at various scales. When species populations decrease, it often disrupts food webs. For example, if predators decline, it can lead to an overpopulation of their prey, causing trophic cascades that affect entire ecosystems. Similarly, the loss of keystone species—those that play a critical role in maintaining ecosystem balance—can lead to habitat changes and a breakdown in the structure and function of communities. This shows how tightly interconnected species are within ecosystems and highlights the ripple effects that population declines can cause.

At a broader ecological scale, declining populations also affect biodiversity. When species vanish or their numbers drop, it reduces genetic variation, making populations more vulnerable to environmental changes like disease or climate shifts. This can create a cycle of further declines, as ecosystems become less resilient to disturbances. Specialists, or species with very specific habitat or food requirements, often struggle to survive, while generalists may thrive, leading to a less diverse ecosystem. Biodiversity loss harms ecological stability, productivity, and the ability of ecosystems to provide essential services, such as clean water and air.

Additionally, population declines intersect with issues like habitat fragmentation and climate change, which exacerbate these challenges. For instance, when habitats are fragmented, it becomes harder for species to migrate, find mates, or access food sources, leading to localized extinctions. At the same time, species in fragmented or degraded habitats are less able to adapt and evolve, further reducing their chances of survival. The overall decline in population numbers, biodiversity, and ecosystem function underscores the urgent need to address global challenges like habitat loss and climate change to maintain the health and balance of our planet’s ecosystems.

Declines in population will have detrimental impacts on the structure of the community and food webs. If populations of primary producers decrease, the energy moving up the food webs will decrease and will cause trophic cascades throughout the whole community. Declines in prey species can also cause trophic cascades and change what species the predators hunt. There are also keystone species, where if they decline, the whole ecosystem can collapse. Competition rates will increase interspecifically and intraspecifically.

Environmental changes due to human interactions will have severe implications for global adaptation. Since community structures will be severely disrupted, certain evolutionary incentives will drive rapid change in niche acquisition and stability. As a broad rule, generalist species and species that have a high tolerance to disruption will disproportionately compete and hold new ecological niche spaces, possibly meaning that these species will form the base of new evolutionary radiations. Specialist species, however, will greatly suffer with regard to ecological diversity, meaning that rapid disruptions such as climate change will greatly de-incentivize such relationships that require consistent stability.

Humans also suffer from global change and there’s already a struggle to identify solutions to anthropogenic problems that don’t have any negative effects of their own, securing funding for that, and implementing it beyond a theoretical sense. Solutions to anthropogenic problems that affect humans may in some cases make more issues in the ecological sphere. The inverse can be true. Defining issues and solutions can vary over time and space. The significance/impact of a solution is important to consider when considering the different approaches to managing the impacts of global challenges.

Future research should primarily focus on how to mitigate the negative effects of climate change, industrialization, urbanization, and habitat disturbance. In general, we should research how to mitigate the profoundly negative effects we as humans have on our environment in order to implement a sustainable model of living in terms of economics, environmental exchange, and resource exploitation. Cost effective ways of removing pollutants from environments which are stalled due to the extent of which its been polluted, and from there the ecosystem can slowly heal itself.

Ecology is the scientific and philosophical framework in which a sustainable world can be explored, developed, and implemented. In this, continued scientific research into how the global environment can be stabilized while making human needs sustainable is critical with regards to the future well-being of humans. Concepts of management, conservation, and stewardship are critical methods of how we can build a more sustainable relationship with nature.

Pollution

Pollution can integrate into food webs via low trophic level species eating microplastics or polluted food. The pollution works its way up the food chain, bioaccumulating into top predators. Pollution has the potential to cause high mortality rates within an ecosystem. This decrease in populations would therefore decrease the competition among surviving organisms. Conversely, competition would increase if pollution decreases food availability. Pollution can have major effects on predator-prey relationships. Bioaccumulation can cause pollution to build up within a food chain. Pollutants can also cause prey to become weakened and could become more susceptible to predation.

Pollution physically modifies the landscape, for instance in the case of “trash islands”, plastic waste and other pollutants functionally become new landmasses in the ocean. Hazardous chemicals, particularly in the air, groundwater, and aquatic environments, can also drive populations of sensitive species to local extinctions and scatter populations. Pollution influences populations through chemical interactions (toxins) which can kill individuals, influence reproduction rates, damage the ability to reproduce, and cause DNA mutations. It can also remove food sources of the population causing widespread death for specialists causing population collapse and local extinction. Community function would typically decrease due to decreased biodiversity. Competition would favor more pollution-tolerant species, leading to a shift in the structure.

Parasitism increases in polluted ecosystems. With the habitat and native species weakened, it is easier for invasive/parasitic species to establish populations. Pollution lowers biodiversity because non-tolerant species may not survive. Some patches of species will evolve faster than other species. Overall, species that cannot evolve or adapt to pollution will experience a population decline. Plant tissues can be denatured due to pollution. This causes lower levels of photosynthesis which decreases the amount of biomass an environment creates.

Different approaches to mitigating / managing the impacts of global challenges

• Reclamation-  introduce tolerant species. Tear out lawn grass/turfgrass & replace with those tolerant species, and esp. plants that can filter/mediate pollutants in suburbs/urban areas.
• Restoration: pollution removal techniques (chemical, biological, physical) ex: bioremediation, genomic approaches (identifying adapted alleles, CRISPR), selective breeding
• Reintroduction- captive breeding programs with intention of reintroduction (examples: coastal birds, keystone predators like grey wolves, ..)
• Rewilding (restore natural processes): Create wildlife corridors, decrease greenhouse gases in the atmosphere

Many of the suggested approaches overlap and share strategies. For example, oftentimes restoration is needed before reintroduction can occur. An example of restoration before reintroduction can include genomic approaches. If scientists can identify better-adapted populations, find specific genes responsible for improved adaptation, and introduce this gene into a genome, genetically improved species can be reintroduced. Reintroduction utilizes methods like captive breeding programs aimed at returning species, such as coastal birds or keystone predators, to their natural habitats. Rewilding focuses on restoring the natural processes of an ecosystem. This can be done by increasing connectivity through the creation of wildlife corridors, or involvement of programs meant to decrease the greenhouse gases in the atmosphere.