The Quiet Effects of Deforestation

 

Introduction

            Each year, an expanse of forest the size of Panama, full of trees whose roots probably vastly outdate the age of anyone chopping them down, is wiped from the face of the earth (“National Geographic”).  The direct negative effects that large-scale deforestation has on an ecosystem are well documented and, by this point, almost common knowledge; in addition to the physical removal of a large amount of plant biomass, a loss of shelter for animals and insects and an increased runoff of soil also adversely impact the deforested area.  In many countries, governmental bodies have recognized these dangers and have implemented policies such as basic restrictions on residential and commercial expansion designed to minimize the effects of these specific consequences (“Center for Global Development”).  New evidence, however, such as the findings of biologist Oswald Schmitz, suggests that the mass clearing of vegetation can have significant ecological ramifications beyond those directly observed, and these new insights should bring about a fundamental change in the way these policies are designed.

 

Body

            Schmitz’ study, Effects of Predator Hunting Mode on Grassland Ecosystem Function, which was based in New England, highlights the more subtle, indirect effects that deforestation is able to have on a large ecosystem through community interactions.  New England was one of the first regions in the Americas to experience massive deforestation, yet also one of the first to witness massive restorative efforts—as a result, it is currently one of the most densely forested regions in the United States (Boesch).  Despite the pro-restoration policies brought about by this ideological shift, the forest cover and diversity in the region are beginning to decline once again due to sprawling, poorly planned residential and commercial development known as “legal fragmentation”, where development lands are sold in smaller portions and thus allowed to chip away at sections of large forested areas under local laws (Boesch).  As Schmitz demonstrates, this new trend may be having an adverse effect on the remaining forest areas as well as on the newly cleared plots of land.

 

           In his study, Schmitz examines the contrasting effects that two different types of spiders—attacking predator versus sit-and-wait predator—have on their main prey species, grasshoppers, and in turn the effect that these herbivorous grasshoppers have on the abundance and diversity of vegetation in the grassland ecosystem.  This field experiment is conducted over a 3-year period, with 14 replicates of 2.4 cubed-meter plots that all contain the grasshopper species Melanopuls femurrubrum, the plant species Solidago rugosa, and various other plant and grass species native to the area.  Half of the treatments feature an “attacking” spider, Phidippus rimator, while the other half harbor a “sit-and-wait” spider, Pisaurina mira.  Schmitz physically measures the biomass of both groups of plants, the aboveground net primary production, the organic matter decomposition rate, and the nitrogen mineralization rate in all 14 replicates at the end of the three-year period as a deviation from the initial measurement (Schmitz 2008).

 

           One of Schmitz’ most important observations at the end of this period is that the biomass of S. rugosa, which is a competitively dominant plant species in the region, is 168% greater in the treatments which contained P. rimator, the attacking spider, than in the treatments containing P. mira, the sit-and-wait spider (Schmitz 2008).  He hypothesizes that sit-and-wait spiders tend to establish a fixed, conservative behavioral pattern in their grasshopper prey through their consistent wait-in-web style of predation.  This conservative behavioral pattern forces the grasshoppers to feed on the safer yet less nutritious S. rugosa plant (Schmitz 2008).  Contrastingly, the random and dynamic style of predation of attacking spiders causes no such fixed pattern in the grasshopper species, who are thus free to consume other, more nutritious plants and grasses and allow S. rugosa to expand and dominate even more extensively (Schmitz 2008).

 

           Therefore, Schmitz is able to assert from his study that an abundance of sit-and-wait spiders (or at least a relatively equal amount to attackers) is beneficial for the biodiversity of this community, whereas a severe lack can be harmful (Schmitz 2008).  Unfortunately, sit-and-wait spiders—which require more specific conditions for shelter—are more impacted by human-caused environmental changes, such as deforestation, pesticide use, and inorganic fertilizer drain-off, than are their attacking counterparts (Schröder et al. 2008).  With the frequency of these occurrences only increasing in New England as a result of development, it is clear that the adverse effects of attacking spider over-representation should steadily increase as well and result in diminishing plant species diversity for the region as a whole. New England, especially New Hampshire and Maine, is a region which prides itself in and defines itself by its abundant and diverse expanses of forests; despite solid restoration and protection laws in the region, loopholes such as “legal fragmentation” are making some of the strongest environmental protection efforts obsolete (Boesch).  Conservation New Hampshire proposes a reform of local programs to protect against the harmful parcelization of lands to ensure larger tracts of forest will remain intact, which should directly benefit sit-and-wait spiders in the region and indirectly increase the overall plant species diversity (Boesch).

 

Conclusion

            While this proposed action and Schmitz’ study are extremely specific and limited to a miniscule geographic area, the symbolic value of the two can have global impacts; deforestation has been a pandemic for a large portion of man’s civilized history, and it has taken centuries for a full-on counter-movement to take hold and begin limiting the consequences of this practice.  Now, many governments are convinced that their policies of simply “limiting tree-cutting” will be all encompassing to stop the negative effects of deforestation.  Studies such as the one conducted by Oswald Schmitz show that the true impacts of human involvement in non-human ecosystems can never be cured with one simple piece of legislation; ecosystems are unimaginably fragile and interdependent, and a change in just one part of this functioning body can reverberate across all others.  Most importantly, these changes will manifest themselves differently in almost every ecosystem, as unique organisms and environmental histories attempt to adapt to the varying degrees of change imposed upon them by humans.  In order to properly protect against all the potential consequences of any degree of deforestation, federal environmental health programs, such as the EPA, should be broken down and decentralized, with only a small group assigned to detect and enforce necessary regulations for the specific area in which they are located.