During the dry season, the Colorado River has little to no water in it by the time it reaches the Sea of Cortez. Pollution: Freshwater wildlife are most impacted by pollution. Pollutants such as untreated sewage, mining waste, acid rain, fertilizers and pesticides concentrate in rivers, lakes and wetlands and eventually end up in estuaries and the food web. Climate change: The emerging driver of habitat loss is climate change.
Wildlife that need the cool temperatures of high elevations, such as the American pika , may soon run out of habitat. Coastal wildlife may find their habitat underwater as sea levels rise.
Plant native plants and put out a water source so that you can provide the food, water, cover, and places to raise young that wildlife need to survive. Stein, B. Adams and L. Oxford University Press, New York: A groundbreaking bipartisan bill aims to address the looming wildlife crisis before it's too late, while creating sorely needed jobs. Other species cannot do this. Elimination of their ecosystem — whether it is a forest, a desert, a grassland, a freshwater estuary, or a marine environment — will kill the individuals within most species.
Remove the entire habitat within the range of a species and, unless they are one of the few species that do well in human-built environments, the species will become extinct. Habitat loss is a process of environmental change in which a natural habitat is rendered functionally unable to support the species present. This process may be natural or unnatural, and may be caused by habitat fragmentation, geological processes, climate change, or human activities such as the introduction of invasive species or ecosystem nutrient depletion.
In the process of habitat destruction, the organisms that previously used the site are displaced or destroyed, reducing biodiversity. Biodiversity loss in Sumatra : a One sub-species of orangutan is found only in the rain forests of Borneo, while the other sub-species of orangutan is found only in the rain forests of Sumatra.
These animals are examples of the exceptional biodiversity of c the islands of Sumatra and Borneo. Other species include the b Sumatran tiger and the d Sumatran elephant, both of which are critically endangered. Human destruction of habitats has accelerated greatly in the latter half of the twentieth century.
Natural habitats are often destroyed through human activity for the purpose of harvesting natural resources for industry production and urbanization. Clearing habitats for agriculture, for example, is the principal cause of habitat destruction. Other important causes of habitat destruction include mining, logging, and urban sprawl.
Habitat destruction is currently ranked as the primary cause of species extinction worldwide. Consider the exceptional biodiversity of Sumatra. The neighboring island of Borneo, home to the other sub-species of orangutan, has lost a similar area of forest, and forest loss continues in protected areas. The orangutan in Borneo is listed as endangered by the International Union for Conservation of Nature IUCN , but it is simply the most visible of thousands of species that will not survive the disappearance of the forests of Borneo.
The forests are being removed for their timber, and to clear space for plantations of palm oil, an oil used in Europe for many items including food products, cosmetics, and biodiesel. A five-year estimate of global forest cover loss for the years — was 3. In the humid tropics where forest loss is primarily from timber extraction, , km 2 was lost out of a global total of 11,, km 2 or 2.
In the tropics, these losses also represent the extinction of species because of high levels of endemism. In temperate and boreal regions, forest area is gradually increasing with the exception of Siberia , but deforestation in the tropics is of major concern. Sustainable practices, which preserve environments for long-term maintenance and well-being, can help preserve habitats and ecosystems for greater biodiversity. Sustainability is a concept that describes how biological systems remain diverse and productive over time.
Long-lived and healthy wetlands and forests are examples of sustainable biological systems. For humans, sustainability is the potential for long-term maintenance of well-being, which has ecological, economic, political, and cultural dimensions.
One approach is environmental management, which is based largely on information gained from earth science, environmental science, and conservation biology. A second approach is management of human consumption of resources, which is based largely on information gained from economics.
A third, more recent, approach adds cultural and political concerns into the sustainability matrix. Loss of biodiversity stems largely from the habitat loss and fragmentation produced by human appropriation of land for development, forestry and agriculture as natural capital is progressively converted to human-made capital. At the local human scale, sustainability benefits accrue from the creation of green cities and sustainable parks and gardens.
Similarly, environmental problems associated with industrial agriculture and agribusiness are now being addressed through such movements as sustainable agriculture, organic farming, and more-sustainable business practices. Overharvesting threatens biodiversity by degrading ecosystems and eliminating species of plants, animals, and other organisms.
Overharvesting, also called overexploitation, refers to harvesting a renewable resource to the point of diminishing returns. Ecologists use the term to describe populations that are harvested at a rate that is unsustainable, given their natural rates of mortality and capacities for reproduction.
The term applies to natural resources such as wild medicinal plants, grazing pastures, game animals, fish stocks, forests, and water aquifers. Sustained overharvesting can lead to the destruction of the resource, and is one of the five main activities — along with pollution, introduced species, habitat fragmentation, and habitat destruction — that threaten global biodiversity today.
All living organisms require resources to survive. Many plants also rely on animals, particularly ones that eat fruit, for seed dispersal. Destroying the habitat of animals of this type can severely affect the plant species that depend on them. Biodiversity affects climate mainly through regulation of the amount of carbon dioxide in the atmosphere.
Destruction of forest habitats reduces the capacity of forests to absorb carbon dioxide. The growth rate and woodiness of a plant determines the rate of carbon turnover within it. Landscape patterns are also important since carbon sequestration is reduced at the edges of forest fragments. Marine ecosystems also play a significant role in carbon sequestration. Pests often target specific types of plants. When habitats are destroyed and plant diversity is reduced, the environment contains more of a particular type of plant.
This makes it easier for pests to spread. There were articles focused on community ecology, with most articles from Latin America and the fewest from Southeast Asia. The best studied taxa were vascular plants followed by insects and birds Table 2. Most studies used species richness and species composition beta diversity to measure the impacts of environmental change, with only a few measuring functional diversity Figure 4A. Table 2.
Number of articles on the impact of habitat degradation of tropical montane forests at various ecological levels distributed across regions, impact types and taxonomic groups. Figure 4. A Number of published articles on the impacts of habitat degradation on tropical montane biodiversity using different community response metrics. The proportion of articles showing the community responses to deforestation and habitat disturbance measured using B species richness; and C species composition.
The numbers in parentheses refer to the number of articles for each type of response. Of 69 articles on ecosystem services, most were from North America largely from Mexico; Table 2.
Ecosystem services were broadly classified as water regulation including erosion control and purification, maintenance of soil fertility, carbon storage and sequestration, and nutrient cycling. Each category was well-represented, with a slight bias toward articles exploring hydrological impacts and soil fertility Figure 5A. Figure 5. Number of articles published on the impacts of habitat degradation on tropical montane biodiversity studying different types of A ecosystem services, and B species interactions.
The impacts measured were almost equally represented, with edge effects slightly more studied than deforestation, land conversion or fragmentation Table 2. Studies on predation often lacked identification of the predators, due to the rarity of documenting such events. Population ecology i. Survival rates and fitness-related traits e. To assess the conservation statuses of species in the population studies, we omitted two articles that measured demographic parameters but with a greater focus on community level responses Hitimana et al.
Figure 6. Number of population ecology articles published on the impacts of habitat degradation on tropical montane biodiversity that: A measured different demographic parameters, and B studied species listed in the various categories of the IUCN Red List.
Only 12 articles described genetic studies Table 2. The earliest study from explored the impacts of habitat degradation logging on the genetics of an endemic species of oak in China Zheng et al. Other genetic studies were published from to , with six from Latin America, four from Africa and one from Asia Table 2.
Most explored the impacts of habitat degradation on a single focal species, but two drew comparisons between two species Winkler et al. Most articles examined the impact of fragmentation or edge effects on genetic diversity or gene flow, while a few studied the effects of deforestation or land-use change Table 2. A myriad of habitat degradation effects on biodiversity and ecosystem services in TMFs were reported Figure 7.
Equivocal or inverse responses in species richness may be due to sampling in habitats with intermediate levels of degradation, which often show higher species richness than pristine environments e. The main cause cited was higher resource availability e. Changes in species composition across a disturbance gradient were often reported, with resilient species more likely to be generalists e.
Figure 7. Schematic of the major effects of habitat degradation on tropical montane forest across levels of organization. The degradation of TMF can be detrimental to some species interactions such as predator-prey e. Increased predation of seedlings was observed in deforested areas due to a lack of concealment from predators Anthelme et al.
Habitat degradation also interfered with mutualistic relationships between plant and soil microbes. For example, plant growth showed a positive response to soil filtrate from TMF due to the presence of beneficial soil microbes, but was negatively affected by soil filtrate from pastures Pizano et al.
Parasitic infections generally intensified with increased habitat disturbance. Amphibian chytrid fungus Batrachochytrium dendrobatidis was most prevalent in agroforests Murrieta-Galindo et al. There were a small number of TMF articles that have investigated how populations respond to habitat degradation. From these studies, habitat fragmentation was shown to reduce the population size of birds and foxes Husemann et al.
For example, the effective of population sizes of the mountain white-eye Zosterops poliogaster in East Africa were higher in larger and interconnected forest patches Husemann et al. Habitat fragmentation can also decrease fecundity in plants Somanathan and Borges, ; Franceschinelli et al.
Fragmentation also resulted in reduced plant survival which could be attributed to higher desiccation and seedling predation Alvarez-Aquino et al. Trees in isolated patches were also found to be to have altered plant sex ratios apart from natural populations due to a lack of pollinator visits to female trees Somanathan and Borges, While genetic studies conducted in TMFs were rare, most revealed that populations in isolated forests had lower genetic diversity due to inbreeding and reduced gene flow Cascante-Marin et al.
For example, a lack of genetic variation in epiphytic bromeliad Guzmania monostachia populations in Costa Rican forest patches was attributed primarily to anthropogenic barriers to gene flow but could also be influenced by life history traits such as its selective breeding system and limited seed dispersal ability Cascante-Marin et al.
Habitat degradation in TMFs has been shown to disrupt several hydrological processes like affecting water conduction in soils, with reduced hydraulic conductivity in secondary forests and plantations Marin-Castro et al. In turn, this likely contributed to increased surface runoff in cultivated land Lorup and Hansen, ; Munoz-Villers and McDonnell, ; Suescun et al. With increasing surface water runoff, streamflow in degraded landscapes can be higher following rainfall Munoz-Villers et al.
Water storage was also lower in agricultural areas Guardiola-Claramonte et al. Land conversion in TMFs can lead to declines in mean carbon densities due to biomass loss De Jong et al. Impacts of land conversion on soil organic carbon SOC are less conclusive; most studies reported lower SOC in cultivated land relative to montane forest e. Such conflicting results may be attributed to variation in soil properties, age since disturbance, the type of cultivated land, and altitude Twongyirwe et al.
Habitat degradation in TMF can lead to marked changes in N storage and conversion rates. Total dissolved nitrogen was higher in plantations than in TMF catchments, probably due to more leaching Jacobs et al.
Additionally, the rate of N decay from leaf litter in plantations, or in streams within pastures, was slower compared to natural TMFs Encalada et al. Land use change alters the properties of montane soils, such as decreasing soil moisture Schrumpf et al. Soil microbial biomass generally declines as land disturbance intensifies Campos et al. Macroinvertebrate diversity in soils is lower in deforested sites Yankelevich et al.
Our method of gauging research effort per country, by aggregating the number of studies stemming from the country of interest, is likely biased by the extent of TMFs available. Estimating the number of studies per area unit of TMF in each country will provide better resolution.
Another caveat to note is that community responses were tabulated without accounting for the intensity of disturbance, beyond broad classifications of habitat types. Also, our classifications did not consider spatial differences among studies, and the impacts of habitat degradation at a site, country or regional scale will vary.
Last, our assessment of articles covering ecosystem services mainly focused on those that provided supporting and regulation services, with less emphasis on provisioning and cultural services Alcamo and Bennett, A separate systematic review on the impacts of habitat degradation on the ecosystem services provided by TMFs is recommended by using additional search terms e.
Average annual deforestation rates from to for montane forests in Southeast Asia ranged from 0. While roads are essential for economic development, they are a major threat to biodiversity Laurance et al.
In Peninsular Malaysia, the construction of the second East-West highway, completed in , has led to rampant deforestation in the Lojing Highlands despite regulations that restrict logging above 1, m Singh, Much of the cleared land has been converted to agricultural farms Omar and Hamzah, Alarmingly, nearly half of montane primary forest loss in Indonesia has occurred within protected areas Margono et al.
To tackle illegal logging, Malaysian and Indonesian governments have implemented schemes that award certification to producers that promote sustainable logging practices e. However, such initiatives have not stopped deforestation of protected areas Peh et al. Imposing sanctions on non-compliant timber producers, and stricter assessments to gain certifications are needed to secure the remaining TMFs in Asia Chitra and Cetera, Research in African TMFs was also poorly represented globally, yet much of Africa's TMF is threatened from overexploitation through illegal logging and poaching, and habitat loss via land conversion to agriculture and charcoal burning Cronin et al.
Although there are designated protected areas in Africa, their coverage is inadequate and many protected sites are poorly managed Cronin et al. Further, the heavy reliance of fertilizers in farms increases nutrient loads in streams that lead to a deterioration in water quality and eutrophication Jacobs et al.
Political unrest in countries such as Sudan also affect the state of natural resources, such as those in the Imatong Mountains and surrounds which are part of the Eastern Afro-montane ecosystem—considered to be one of Africa's biodiversity hot spots Uma, Two decades of civil war have decimated large swathes of forest, particularly on Mount Dongotomea, with two-thirds of the forest lost since Gorsevski, ; African Wildlife Foundation, A lack of livelihoods for returning refugees and strong dependence on natural resources has led to increased poaching for bushmeat, illegal logging and fires set deliberately for shifting agriculture Gorsevski, ; African Wildlife Foundation, Articles describing research conducted in Mexico comprised a third of all relevant papers in this mapping exercise.
Deforestation rates in the highlands of Mexico have also intensified sharply Cayuela et al. In the Chiapas highlands, the annual rate increased from 1. More recent estimates of TMF deforestation rates are lacking in Mexican TMF, and considering that the last reported deforestation rates were rising nearly two decades ago, an updated estimate is crucial to assess the current extent of forest loss and re-valuate its impact to montane biota. These included changes in species distribution and population sizes, germination and seedling development, community structure, food webs and nutrient availability.
For example, the altitudinal distribution of several dung beetle species was higher in deforested areas where it was hotter and drier than in intact landscapes Larsen, Harsher microclimates in altered habitats negatively affected germination rates, seedling development and recruitment, which in turn hampered recolonization rates Werner and Gradstein, ; Anthelme et al.
Epiphyte species richness declined due to warmer and drier microclimates in disturbed forests Barthlott et al. Clearly, the most urgent research priority with regards the impacts of habitat degradation on TMF is to understand its effects on population genetics Figure 8.
Aside from there being so few genetic studies of species occurring in this forest type, the preservation of genetic diversity is fundamental in maintaining viable populations that have adaptive potential. We suggest applying next-generation sequencing NGS in future genetic research, as inferences from NGS are drawn genome-wide Angeloni et al.
This is unlike the studies identified via our systematic map, where traditional methods like Sanger sequencing or microsatellites targeted only a few genes. Figure 8. Research priorities for conserving the world's tropical montane forest ecosystems, indicated in order of importance. A logical group for thorough evaluation of their genetic structure are threatened or endemic species, many of which are likely to exist as small populations that are vulnerable to the effects of genetic drift.
The findings from the limited number of studies conducted in TMF have shown expected results: 1 habitat fragmentation can impede gene flow and lead to a loss of genetic variation, and 2 , improving fragment connectivity can help reserve this trend.
Where possible, drawing inferences on gene flow and genetic diversity from multiple species within an ecosystem is ideal, as species responses to fragmentation can differ in concert with variation in species traits. For instance, a study of montane forest birds in Kenya revealed tighter genetic clustering among sedentary species compared to more mobile species Callens et al.
Further, generalist species are often more robust to the impacts of habitat fragmentation Janecka et al. Not yet documented in our mapping exercise are studies that examine the role played by habitat degradation and likely interactions with climate change on introgression in TMF biota.
Introgression is the hybridization of closely related species accompanied by repeated back-crossing of the hybrid with a parent species Anderson, It is pervasive in natural populations and can accelerate the loss in genetic diversity Harrison and Larson, A study in the Ethiopian highlands found that the wild gene pool for Coffea arabica had admixed with cultivars grown in close proximity to natural populations Aerts et al.
If so, montane endemics may experience genetic swamping i. Research that investigates the impacts of habitat fragmentation and edge effects on montane biota should also be prioritized, as the results will have profound implications for sustainable land-use planning e.
Although fragmentation is well-known for reducing gene flow, it has far-reaching consequences at all ecological levels, including ecosystem services.
In general, fragmentation has a negative impact on communities; resulting in a decline in species richness e. However, some studies have highlighted that certain spatial characteristics such as fragment area and isolation have no effect on abundance, density or diversity Muriel and Kattan, ; Ulrich et al. While the extent of degradation may lead to conflicting results, deeper examination of species functional traits, which are indicators of habitat use, reveal that some groups within a community are more affected than others.
For instance, two avian studies independently concluded that understory insectivores and canopy frugivores were more sensitive to fragmentation than other functional groups Kattan et al. Thus, within-community differences should be accounted for in future fragmentation research in TMF. Our current understanding of the long-term effects of fragmentation is also limited by the scarcity of relevant historical data.
In the short term, diversity may not be adversely affected by fragmentation and may even increase Rey-Benayas et al. Elucidating the environmental factors driving colonization and extinction patterns will allow better comprehension of community dynamics in a fragmented landscape. Both are hierarchical models, but the dynamic model accounts for changes in occupancy over time by including sub-models of colonization and persistence that affect the previous occurrence state.
Crucially, DCM models do not assume perfect detection among species, which can lead to misconstrued interpretations of occupancy dynamics. A key recommendation from our mapping exercise is that effects of fragmentation should be examined at multiple spatial scales, as scaling dependencies in fragmented landscapes are vital for conservation planning Cushman and McGarigal, While broad spatial effects have been documented to affect biotic responses Chiavacci et al.
For example, research on golden-cheek warblers, Setophaga chrysoparia , showed that landscape composition best predicted species density, but vegetation characteristics was the best predictor of nesting success Reidy et al. Region-wise, research in Asian TMF is under-represented at all ecological levels, impact type and taxa Figure 8. The future discovery of new species is particularly likely in Southeast Asia, given the regions' unique biogeographical history Holloway and Hall, In the last 5 years, several new species were discovered in TMFs in Southeast Asia, including amphibians and reptiles from Vietnam Grismer et al.
In these regions, attaining baseline ecological data such as a country-by-country species inventory represents a crucial first step in efficient data-sharing, and accumulation of large databases that facilitate multidisciplinary ecological research.
Although we encourage further research of poorly studied taxa, available data for better represented groups such as vascular plants and birds are already useful for comparative studies, and to gain perspective on the overall response of the biome to habitat degradation Figure 8. Comparisons between the responses of endotherms and ectotherms will be of interest, as the latter are more likely to be adversely affected by degradation due to their sensitivity to microclimatic change and generally lower dispersal abilities.
Greater attention should be given to how functional diversity, which characterizes the range of ecological roles played by species in a community, may be affected by anthropogenic change in TMFs Petchey and Gaston, Species richness estimates and related indices assume all species perform the same roles, but high species richness does not necessarily beget high functional diversity Stuart-Smith et al.
For example, while bird species richness and density in medium-sized fragments were higher than larger fragments in Mexican TMFs, larger fragments had a distinct functional composition, with a greater proportion of understory insectivore species and canopy frugivores Rueda-Hernandez et al. Furthermore, functional diversity may be a better predictor of ecosystem function than species richness or abundance indices Gagic et al.
Applying an ecological network is a useful approach to test the effects of degradation on species interactions at the community-level. An ecological network is a collection of nodes represented by species that are joined by links that either represent antagonistic or mutualistic interactions Pascual and Dunne, The resilience of ecological networks can be compared along a disturbance gradient Harvey et al. In one study, seed-dispersal networks of birds in the montane forest interior and edge were compared, revealing that functional and interaction diversity were higher at forest edges Saavedra et al.
Such conflicting responses to habitat degradation may relate to different levels of disturbance in these networks i. As montane species are highly sensitive to disturbance Long, ; Brooks et al. The lack of population studies of TMF species in Southeast Asia is troubling given that the number of montane species threatened with extinction in this region may be underestimated Brooks et al.
Indeed, some NE species may be included in national threatened species lists, however, evaluation against IUCN Red List criteria is crucial for formulating policy and prioritizing management of threatened species at multiple scales e. Disappointingly, only a few articles investigated the effects of habitat fragmentation or edge effects on ecosystem services in tropical montane environments Table 2. Factors such as fragment size and isolation can influence ecosystem services; for example, regulation of crop pests is more effective next to a forest, but crop production is greatest at intermediate distances from a forest Mitchell et al.
Careful consideration of the ecosystem services affected by fragmentation is crucial, as trade-offs between different services can be expected. For instance, in a study of montane heathlands, decreasing fragment size reduced biodiversity and recreational value, but increased carbon storage and timber value Cordingley et al. The framework provided by Mitchell et al. Our systematic map has shown that habitat degradation in TMFs has had discernible impacts on biodiversity and ecosystem services.
While the impacts of this degradation are fairly well-studied at the community level, and adequate data may be available for meta-analysis, the impacts on genetic diversity and gene flow are less well-understood.
Thus, population genetic studies should be prioritized for endemic species that are extinction-prone. We also advocate studying the long-term impacts of habitat degradation particularly habitat fragmentation on TMF at multiple spatial and taxonomic scales, and greater support for research based in Asia and Africa.
MS and KP conceived the systematic mapping. MS and CB performed the literature search and data extraction. MS wrote the manuscript and all co-authors reviewed the manuscript.
The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. Abella-Medrano, C. Spatiotemporal variation of mosquito diversity Diptera: Culicidae at places with different land-use types within a neotropical montane cloud forest matrix. Vectors Aerts, R.
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