Habitat change from disruption of ecosystem processes

By Tia Rose MSc.     


     Ecosystem processes are the physical, chemical and biological actions and events that link organisms and their environment. They include decomposition, production of plant matter, and nutrient cycling. These processes act as services, providing us with food, clean drinking water, and pharmaceuticals. They also regulate climate, sequester carbon, pollinate our food crops, and recycle water and minerals within every environment. Ecosystem processes can also include a cultural benefit, such as recreation, scientific study, and spiritual inspiration. They keep the community dynamics of the environment healthy and the flow of energy consistent.

     Biodiversity and a functioning ecosystem is fundamental to the health of the environment. The impact humans have on the environment have shown to cause general decline in diversity and predictable shifts in ecosystem functionality *1. The change in ecosystem composition is caused by introduction of species, species extinction, nitrogen deposition, fragmentation, predator decimation, and alternative management practices *2. Inadequate management of the landscape is a direct effect on the environment by humans and is the leading cause of desertification worldwide *3.

     The most widely published case of ill land management, that lead to desertification, was the Dust Bowl in America during the great depression area. Precipitated by the 1862 Homestead Act, a wave of new settlements and farm cultivation spread across the western plains of America. Deep plowing, over-grazing from cattle farming, and several droughts at the beginning of the 20th century eroded the virgin top soil so severely that millions of acres of farmland became useless *4. Dust storms from high winds lifted the dried soil, blocking out the sun for days at a time, became known as ‘Black Blizzards’. The ecosystem service, prairie grasslands provided by holding soil in place and prevented loss of water moisture from evaporation, had been destroyed. Before the devastating farming that started in the late 1800’s, the American Great Plains were the largest biome in the world next to the Boreal Forest *5.

     By 1935 New Mexico, South Dakota, North Dakota, Oklahoma, and Colorado had the highest percent of family farms on relief, most of which were on the Plains of those states *6. The product of misguided agricultural policy and unregulated settlement of the land, the Dust Bowl in 1934 was the ecological consequence of earlier decades of too-assertive agriculture *6. Today the United States is the fourth most severely affected country by land degradation worldwide and recent droughts have increased vulnerable areas, prone to desertification, by 2% *7. Globally, land degradation affects 1 billion people and every year it gets worse, with an estimated 20 million hectares of arable land being lost annually *7.

April 18, 1935 Dust storm approaching Stratford, Texas. Dust bowl surveying in Texas Image ID: theb1365, Historic C&GS Collection. Credit: NOAA George E. Marsh Album

     The world should have heeded the warning from these devastating events, but many developing countries, such as China, have not learned the lesson. In the last 40 years, northern China’s rates of desertification have reached as high as 1.64% with 65.51% of the arid and semi-arid lands becoming deserts *8. In 1995 it was reported that the total cost to China was 600 million USD. However, worldwide that cost sky rockets to USD 40 billion annually *7. Not included in these costs is the need for increased fertilization, poor health, malnutrition, and the loss of biodiversity *7.

     The loss of biodiversity through disruption of ecosystem processes is not restricted to the terrestrial environment. Marine biodiversity loss is increasingly diminishing the ocean's capacity to provide food, maintain water quality, and recover from distresses *9. The over-exploitation of marine resources has a strong top-down force that often has far reaching effects on ecosystem structure and function. The functional diversity of the marine ecosystem has shown that as resources disappear, diversity declines sharply along with the ability to recover, stability in the ecosystem, and water quality *9. The reverse has also shown to be true, increasing biodiversity increases productivity and stabilizes the ecosystem *9.

'Conservation is a state of harmony between men and land.' - Aldo Leopold  

Resources: Habitat Change and Disruption of Ecosystem Processes,  Prioritizing rehabilitation activities,  Rhythm of conservation.

          Are we making new mistakes or the same old ones?

  

 

 

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Habitat Destruction and Fragmentation

By Tia Rose MSc.    

      Habitat destruction is the leading cause of species extinction today *1. The forces that drive habitat destruction and fragmentation are largely due to human actions through harvesting of natural resources for industrial production. Examples of this are mining, logging, trawling, urban sprawl and, most destructive, agriculture. As the human population has grown, so has the need to provide food and lifestyle for that population. Agricultural activity has dramatically altered our planet’s land surface*2 and nowhere is that more obvious than in the tropics.
     
     Recent history tells us tropical nations have among the highest population growth rates in the world. ‘The population of Latin America, for example, nearly tripled between 1950 and 1990, rising from 166 to 448 million residents’ *3  

Forest destruction during the 1980's in six tropical countries. 'When tropical nations are compared, there tends to be a strong, positive relationship between populations size and annual rates of deforestation" *3

      
     One of the most famous examples of human population growth leading to species extinction is of the Javan tiger (Panthera tigris sondaica). This subspecies of tiger once flourished on the island of Java, found nowhere else in the world, the population began a steep population decline as the human population grew. Habitat loss from agricultural development and urban/village growth reduced the Javan tigers’ range, constraining the population to remote forests and mountains by the 1940’s. Competition for shared prey species often resulted in direct hunting and poisoning of tigers, decimating the population even further.

     Once so abundant that they were considered pests in some areas, an estimated twenty to twenty-five individuals of Panthera tigris sondaica remained by the mid-1950's. In 1980 the World Wildlife Fund (WWF) and the International Union for Conservation of Nature (IUCN) published a management plan for the Javan tiger in Meru-Betiri reserve, a rugged area in southeastern Java. At the time of the report, there were no more than four or five individuals left of the wild population *4. It is believed that the Javan tiger went extinct shortly after this, though the exact time of extinction remains unknown and unconfirmed sightings of tigers still occur in Meru-Betiri National Park today.

     Habitat loss is just one side of a double edged sword. Even today, if a few remaining Javan tigers exist; the small population and range, constrains them from rebounding successfully through lack of abundant resources and increased inbreeding. As a species’ population decreases, so does the genetic variability and with that goes the future health of a population; when this happens a population genetic bottleneck occurs.

     Genetic bottlenecks can also occur when the habitat range of a species is fragmented and populations are divided from each other. The industrial revolution, that was brought about by the sudden boom in human population, has caused habitat fragmentation with the development of transportation infrastructure *5, agricultural lands, and cities. These create physical barriers to species’ dispersal and can increase the rate of loss through death from vehicle strikes, human interactions, and ultimately loss of gene flow.

     
     Undeveloped regions of habitat are rare and many remaining wild species that exist in these habitats are fragmented populations. Species with highly restricted ranges are at a greater risk of extinction; this inherent weakness is the main reason that so many island species have gone extinct or are endangered *6. The minimum amount of habitat required for a population of a particular species to last in an environment is the ‘extinction threshold’ *7. As habitat declines, mortality rates increase and habitat fragmentation is believed to increase the extinction threshold for species that requires greater range of habitat to exist. Extinction threshold is affected by overall rates of colonization and extinction in a landscape and the rates of birth-immigration-death-emigration (BIDE) to a patch of habitat *7.

     Habitat fragmentation can lead to loss of genetic variability and possibly to the extinction of local populations *5, as in the case of the flightless violet ground beetle, Carabus violaceus, whose populations range is restricted to patches surrounded by roads and highways that inhibit the movement of individuals to neighboring populations. Migratory species, such as birds and butterflies, can be especially affected if the habitat destroyed is the home range, breeding ground, or an away point between the two. Disrupting the gene flow from migratory species in this way has been shown to be detrimental to their populations *8.

     Habitat destruction is a serious threat to biodiversity, the loss of which ultimately becomes detrimental to humans. The clearing of tropical forests for cultivation of crops or grazing for animal production is responsible for up to a quarter of the total emission of carbon dioxide into the atmosphere and nearly a third (1/3) of the available surface water on earth is used for irrigation *3. The loss of natural ecosystem services, that is crucial for maintaining rivers and watershed, stabilizing soils, and preventing massive erosion, is reshaping landscapes and rearranging weather patterns.

“Earth provides enough to satisfy every man's needs, but not every man's greed.”
― Mahatma Gandhi 

Resources: Tha Habitat Loss Game, The Loneliest Animals, Ya gotta lichen Carbou, Space for species  

If traditional agriculture was based mainly on food for humans, what do we call the new agriculture based on biofuels, cosmetics and food for livestock? Lifestyle Agriculture? Is this sustainable? 

 

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References: 

1. Pimm, S. L. a. R., Peter. (2000). Extinction by numbers. Nature, 403, 843-844. 
2. Ramankutty, N. E., A.T., Monfreda, C. and Foley, J.A. (2008). Farming the planet: 1. Geographic distribution of global agricultural lands in the year 2000. Global Biogeochemical Cycles, 22.
3.  Laurance, W. F. (1999). Reflections on the tropical deforestation crisis. Biological Conservation 91, 109-117.
4.  Seidensticker, J., et. al. (1980). The Javan tiger and the meru-betiri reserve: a plan for management. Gland, Switzerland: World Wildlife Fund and International Union for Conservation of Nature.
5.  Keller, I. a. L., Carlo R. (2003). Recent habitat fragmentation caused by major roads leads to reduction of gene flow and loss of genetic variability in ground beetles. The Royal Society, 270, 417-423.
6.  Simberlogg, D. (1995). Habitat fragmentation and population extinction of birds. Ibis, 137(1), 105-111.
7.  Fahrig, L. (2002). Effect of Habitat Fragmentation on the extinction threshold: A Synthesis. Ecological Applications, 12(2), 346-353.
8.  Williams, B. L., et. al. (2003). Landscape scale genetic effects of habitat fragmentation on high gene flow species: Speyeria idalia (Nymphalidae). Molecular Ecology, 12, 11-20. 

How has Human Overpopulation Caused Major Loss of Global Biodiversity?

By Tia Rose MSc. 

     Thomas Malthus, the eighteenth century political economist, demographer, and creator of the Malthusian theory, said ‘that the power of population is indefinitely greater than the power in the earth to produce subsistence for man’. Centuries later and a couple billion people more, Paul Ehrlich expressed the opinion, in the 1968 bestseller The Population Bomb, ‘[the] world’s population increased, not because people were breeding like rabbits, but because they stopped dying like flies’. In fact, our current human population adds to itself by roughly 74 million people per year, estimating our total population to reach 9.2 billion by 2050.

     Populations are always in a state of fluctuation, growing and collapsing based on resource availability. A simple example of this can be seen in yeast that is introduced into the sugary environment for wine or beer making. The population of yeast grows exponentially until the sugar, or nutrients are all used up, or the environment becomes too toxic, and the yeast population begins to die off and collapse. Just as the sugar provided for the yeast, fossil fuels have provided humans with the ability to exploit an overwhelming array of resources and made it possible for rampant population growth. However, just as with the yeast and the sugar, resources on this planet are beginning to dry up and disappear. Oil AND water are becoming increasingly scarce, land for agriculture is harder to come by, and many of the other species with which we share this planet are going extinct.

     Anthropogenic Extinction is the term given for the current mass extinction brought about by humans. The cause of which is due to major loss of global biological diversity through habitat destruction and fragmentation, habitat change from disruption of ecosystem processes, introduction of invasive species, pollution and over-exploitation. On land it is estimated that 34% of the planets ice-free terra firma is being devoted to human agriculture, 12% for cropland and 22% for pasture, leaving very little for biodiversity and ecosystem processes that are necessary for a healthy environment. In the ocean, due to over exploitation and increased demand for an ever-growing human population, 90% of predatory fish are gone from the world’s oceans.

Figure 1: ‘The increasing rates of change in human activity since the beginning of the Industrial Revolution. Significant increases in rates of change occur around the 1950s in each case, and illustrate how the past 50 years have been a period of dramatic and unprecedented change in human history’ (Scientist, 2008)

Figure 1: Special Report: The facts about overconsumption. 

 

     The environmental effects of human over-population include habitat destruction and fragmentation, habitat change from disruption of ecosystem processes, over-exploitation, introduction of invasive species and pollution. These topics shall be highlighted in future post.

The important thing is not to stop questioning. -Albert Einstein

 What is Biodiversity? 

 

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