Understanding Clear Cutting and Sustainable Forestry Practices

hi everyone welcome to this PowerPoint on clear cutting and sustainable Forestry

we're going to be talking about two learning objectives today they're pretty much contrasting learning objectives uh

topic 5.2 which is clear cutting and topic 5.17 which is sustainable forestry and you can obviously see how they are

related to one another the enduring understanding for the first is that humans use natural resources they alter

the natural system and we're going to be describing the effects that clear cutting has on those natural systems

specifically forests and for topic 5.17 humans can mitigate their impact on land and water resources through sustainable

use and describe methods of mitigating human impacts on forests the vocab is listed here but I'm going

to skip it and if we were in class we would do this think pair share but pause this right now and think about some of

the ecosystems services provided by forests we've already gone through many of these so you should be able to recall

some now that you've had a moment to think about that let's talk about those

ecosystem Services provided by forests first off about a third of Earth's land surface is

covered by Forest much of that is boreal forest in the northern hemisphere as well as large swaths of tropical

rainforest the largest of which is the Amazon rainforest and then you have temper deciduous forests and tropical

dry Force as well a lot of earth's surface is covered by Forest not as much as sometimes in the past but still a lot

so they are very very important and they play an outsized role in many of the biogeochemical cycles specifically the

carbon cycle trees obviously have more biomass per individual than grasses do so there's

more biomass and therefore more carbon compounds in that tree than there is in an individual grass

so photosynthesis obviously is going to lead to vegetation being a carbon sink that vegetation lives and is a carbon

sink and then that dead vegetation is also a carbon sink you have all that carbon that's locked in organic

molecules in the dead vegetation until it decomposes and then you also have humus and soil carbon

all right the hydrologic cycle sorry the Bell just ran the hydrologic cycle a couple of the most more

important things transpiration obviously this is not an exhaustive list but transpiration okay recall that

transpiration is water that's evaporating directly from the stomata or the pores in leaves of plants

and that water can lead to cloud formation in fact it's estimated that about a third to a half of all the cloud

formation um and the Amazon rainforest is due to transpiration alone not brought in from

um evaporation from Over the oceans but transpiration alone and it also creates Cooling in that

local area remember that whenever water evaporates whether it's transpiration or just evaporation combined that with the

evapotranspiration whenever water evaporates it cools that surface that it's evaporating from so there's a

cooling effect from transpiration as well um tree roots and the understory plants

in the forest help reduce runoff and increase the percolation of groundwater into the soil we talked about this with

watersheds and why Mountain forests upslope of um of agricultural land or upslope of cities is extremely important

for providing a constant supply of water for those human activities or infrastructure and then Sephora soils

filter water as well and then for nitrogen phosphorus Cycles they obviously cycle those nutrients but it's

not as big of a player here as the carbon hydrologic Cycles some other ecosystem Services uh there

is some overlap here so soil formation retention they filter pollutants out of the air and water so trees will filter

pollutants out of the air through the process of photosynthesis and then um you know some other biochemical

Pathways that we don't really have to get into but they also filter pollutants out of water in the soils okay they can

recharge the groundwater so again that infiltration they provide habitat for all the organisms in the forest all the

different species primary productivity is huge and they moderate the local climate again there's the shade they

moderate the Albedo they reflect some sunlight opposed to dark soil which would absorb more sunlight and then

although trees do absorb a lot of sunlight and they only have a very moderate of Albedo they just reflect a

little bit of sunlight and then there's the transpiration I talked about on the last slide

this shade component is huge and I've seen that come up on a few frqs especially if one of them that we talked

about in class where you might have a river and you clear cut all the trees that

overhang this River and shade this River so you remove those and that shade is no longer cooling that River and that River

heats up in fact I have that on the next slide as well well I guess I didn't have it on this

slide it's uh coming up on a different slide anyway some provisioning Services um Timber obviously we get a lot of wood

from forests that's our primary place where we get wood from uh farming we can Farm in forests so there are certain

crops that are shade tolerant that actually grow better underneath of the canopy of other plants other trees than

they do in full sun coffee is a great example of that so we have shade grown coffee on the left and Sun coffee on the

right um if we grow the same variety of coffee in

both shade and then exposed to full sun the shade ground coffee typically produces more because coffee is an

understory plant it's a mid-canopy plant and it evolved to grow in the shade so it's actually better to grow coffee or

vanilla or chocolate under the shade of other trees than it is out in full sun so replacing a monoculture like we see

on the left are on the right sorry with a more diverse community that can provide some natural habitat on the left

we can do Silva pasture this is really um an underrated thing that Forest can provide and it's really for somewhat

specific for us a a dense tropical rainforest is more difficult to do silvopastering than a tempered deciduous

forest with um a lot of open ground for grasses but we can still do some Silva pasture which is just grazing

um in the forest okay there's obviously a lot of wild caught food sources so we can forage for

mushrooms or berries we can hunt and we can fish and forests and then the potential Pharmaceuticals is a major one

so there is a lot of pharmaceuticals most of our Pharmaceuticals in fact are based off of

um naturally occurring compounds in plants or fungi or even some bacteria there are many many many plants that

modern science has not yet tested that are known to indigenous communities to have pharmaceutical effects and if we

just clear-cut through the entire Forest we may lose those species and those potential Pharmaceuticals

okay and all this brings us to deforestation so we first talked about why forests are

important now let's talk about what we're doing to force deforestation this is the removal of forest and converting

that land to any non-forest use that could be farmland or pasture it could be development it could be mining or

anything else okay clear cutting is slightly different from deforestation they are two different and distinct

terms clear cutting is cutting down all the trees just all the stems in the forest

we will often do that just for Timber extraction and when we'll let the forest regrow and then do it again

but it can also be used to convert that Forest into other forms so deforestation is often accomplished through clear

cutting but clear cutting does not necessarily imply that deforestation is occurring okay we have to look at the

setting or the um the context of that activity okay so these are some pictures of clear cutting obviously we have on

the left in aerial view and then on the right to ground level views of clear cutting all of these look as though

they're from boreal forests okay it's again literally just chopping down every tree and as you go through that entire

process you create all this debris on the ground that Smothers all of the understory plants in a often um often it

does now clear cutting is an umbrella term that encompasses many types of clear

cutting you don't need to know all these what you need to know are standard clear cutting and slash and burn the two that

are in bold but I'm going to go through the rest of them because um I think that awareness of the

different techniques that are out there can help you out understand this entire concept so standard clear cutting is

just removing every tree okay it's what we saw on the previous slides where you just remove every tree and you just go

through the forest and get rid of all the trees okay patch clear cutting though that's removal of the trees in

just a certain area say that we have one patch that we clear cut another patch that we leave open or sorry unclear cut

not open but a closed canopy and then another patch that we clear cut and then another patch that's intact Forest so we

can remove certain patches of Forest for extraction of materials and a and a really cognizant way or a way that

is intentional okay based off of certain characteristics we can do strip clear cutting this is removing all the trees

in a strip that's perpendicular to the prevailing winds so let's say that the prevailing winds are coming out of the

West and we have our forest here we can remove a strip

a forest and then a strip of forest and then a strip of forest perpendicular to the prevailing winds and what that

essentially does is create wind breaks so that all of the soil that's in these patches

that has been clear-cut is protected by the wind from the trees that are remaining in

this area and that soil doesn't um blow away it there there's it

mitigates the the erosion effects of the Wind on that soil okay so a little bit more

environmentally friendly than just standard clear cutting you would typically do this in a um in a

tree farm you would typically say that you plant trees here that are five years old

or maybe 15 years old and then the trees that you harvest are 30 years old

so you would stagger where you harvest with where you plant and then these tree breaks you would

plant those again and new trees the area that you just clear-cut they would grow up and then another 15 years you would

harvest the current wind breaks using um and then the old the new trees and the old clear-cut Zone would be the new

wind breaks okay hopefully that makes sense that was a really poor explanation um

clear cutting with reserves that's where you're removing most of the trees but you're leaving some left for a certain

specific reason maybe those are a value food source so maybe they provide nuts that you can eat maybe you'll leave some

trees for your cattle to get some shade under maybe you'll leave a couple trees because you're forbidden for cutting

them down for whatever reason maybe it's like an endangered species or a threatened tree or it's a um or it's

like the national tree of your country whatever it is maybe there's some symbolic or cultural reason for that for

leaving that one tree or one type of tree and then seed cutting this is removing

the majority of the trees but leaving some left to reseed the forest okay then we get to slash and burn slash

and burn is a little bit um misunderstood because nowadays it's used pretty much in an unsustainable

fashion this is where you convert your Forest to agricultural land um

in the past when human populations were low and we weren't encroaching on forests as much

as we are at the rate that we are today slash and burn was a little bit more sustainable

essentially what you do is let's say that you have a large area that is forested you will

cut down a certain plot you will cut down all the trees in that area use them for whatever purpose you can use that

tree for and then you would burn the rest remember that burning wood releases a lot of the nutrients that are in that

wood into the soil so the phosphates the nitrates in that wood into the soil in fact pot ash or potash is potassium that

you get from Ash okay it's really good potassium source so you would then farm that area leaving the rest of this as

Forest you would Farm it for a few years until you deplete that soil and then you would move on to the next

patch of forest you would clear cut it um and slash and burn it sorry and then

allow this previous patch to start to re-vegetate so it would start to go through the stages of secession

um and re-vegetate and then you would go to the next patch and then the next patch

the next patch Etc working through these patches of forest until you get back to the

original one maybe 15 20 30 100 years later and you would go in the cyclical mantle

Manner and not use a very large amount of forest now the problem nowadays is that slash

and burn is no longer applied in a cyclical manner instead what we're doing is just marching in a linear fashion

through the forest and burning as we go okay because there's so many people and we need so much land to feed the growing

human population especially since so much of the human population is transitioning to a more meat heavy diet

so we need more land to feed all of those people okay

all right so some negative impacts of clear cutting obviously we're going to negate all of the ecosystem all the

ecosystem services that forests provide we lose our habitat and we lose our biodiversity first okay we will

pretty much immediately increase our water runoff and soil erosion through both water and wind even though some of

those methods that I described on the previous slide mitigate that that erosion you still have that erosion

because those trees are no longer there holding the soil okay so this the soil dries out and it can erode via water and

wind because you no longer have Roots holding that soil together okay you increase the atmospheric carbon

especially if you were burning that area but as we saw with the termite frq even the decomposition of all that plant

matter is going to release carbon dioxide into the atmosphere so decomposition combustion and aerobic

decomposition rather is going to release CO2 anaerobic decomposition is going to release CH4 or CO2 depending on the

pathway present but we're typically going to be talking about CH4 being released by methanogenic bacteria

um and again decomposition releases CO2 or CH4 but the carbon content of the soil is going to decrease as well so

that hemis is going to be exposed to the air and it's going to decompose as well plus you have all the Machinery that

burns fossil fuels that is used to accomplish deforestation or accomplish clear cutting and that all releases

pollutants as well including carbon dioxide okay we lose a food source for both

humans and animals if the forest is no longer there if that habitat is no longer there you can no longer hunt in

that area Okay reduction of Tourism you increase the temperature of soil the rivers and all that from the loss of

shade so that's what I was talking about on that previous slide where I had the diagram of the river if there's trees

overhanging that River you cut down all the trees that River temperature is going to increase perhaps out of the

range of tolerance of some of those organisms in that River so continuing on with runoff and erosion

so runoff and erosion are going to become huge in this unit um so because they're increasing

we're going to because erosion is increasing and runoff is increasing all of that water that is running off of the

surface and eroding the soil with it is going to carry that soil that sediment into your local waterways it also is

going to carry anything that's in that soil to your local waterways as well including dissolved chemicals such as

heavy metals or pesticides or nutrients okay that's going to increase or just the sediment alone is going to increase

the turbidity of that water and recall that turbidity is the measurement of suspended solids in a water column

that's going to decrease the clarity of your river which is going to decrease your primary productivity in that

Waterway which is going to impact the food web it also decreases the Albedo so that means that more sunlight is going

to be absorbed by that River or whatever Waterway it is and it's going to increase in temperature in addition to

the loss of shade that the trees are providing the nutrients that are going into the

river the sediment and the nutrients really but if we're talking about sediments being soil soil contains

nutrients but we're also talking about the minerals nutrients and fertilizers that are going into your Waterway that's

going to lead to eutrophication and we've talked about that so many times before that I'm not going to redefine it

here you can change your water chemistry so the water PH being part of that but also

the nutrient load and everything else in the water we'll talk about dissolved oxygen a little bit later on when we

talk about when we talk about water pollution but it's going to decrease the dissolved oxygen in that Waterway as

well especially due to eutrophication and all of that is going to reduce and

loss of habitat and biodiversity in that ocean and then all of those rivers are going to lead to the ocean

sorry I think I said ocean earlier but all the rivers are going to lead to the ocean and they're going to cause these

same effects in the ocean leading to Oceanic dead zones okay and then if we're talking about

mangroves specifically mangroves buffer Storm surges so we're going to lose that buffering effect of of the mangroves

all right some other impacts um because we're clear cutting that's implying that humans are penetrating

deeper into these forests that's going to lead to further habitat fragmentation and increased Edge effect in those

forests this one is a big one introduction of evasive species to that Forest where

it's been clear-cut okay so because humans are moving into that area we are we are taking species with us whether

intentionally or unintentionally even a fungus like kitrid fungus that can survive on the soles of your boots you

walk into an intact Forest walk through a creek and then all of a sudden you've you've introduced kitrid fungus into

that Creek and the amphibians in that Creek can suffer from it zoonotic disease is also big what I'm

showing up here on this diagram we'll talk for an entire couple days about zoonotic diseases but those are diseases

that jump from animal hosts to humans so humans are not the primary host of these diseases but because we're now in

contact with these animals because we penetrate deeper into the forest we are getting these diseases okay HIV is a

great example Ebola is a great example of these diseases and then we can displace indigenous groups groups of

people indigenous groups of people that were already in the forest the Amazon is a great case study for that

so if we have all these negative effects for clear cutting then why do we do it well not surprisingly the answer is

short-term economic benefit okay you're getting money from it you're getting money either from your Lumber or the

fuel wood or charcoal that you can sell you're getting money from raising cattle or soy or corn or palm oil in that area

that was previously forest all of this is just due to economics okay even if like just the most basic idea of you

have to have fuel wood to eat to cook your food because you don't have electricity that is still that that's

another reason okay but primarily it's it's economic so just some figures about deforestation

at the present rate of deforestation we're losing about 28 million hectares of forest a year that is a lot of area

that's equivalent to about one football field every second so if you think about um I just eliminating one football field

every single second and how many seconds there are in a year that is a lot of land every year

okay those current rates continue all the world's forests are going to be lost in 100 years or less and then the stats

that I can find um from this Source we're from 2018 and then we're looking at the highest

loss of primary Forest not surprisingly Brazil is the highest one and then a very distant second the Democratic

Republic of Congo and then Indonesia Colombia and Bolivia okay notice that three of the top five are in South

America the Amazon rainforest and the other rainforests around the Amazon and then Africa the Congo rainforest and

Indonesia so since Brazil is losing the most um Forest around the world let's look a

little bit closer at Brazil now Brazil is a very large country okay so that's one of the reasons that it's um losing

so much Forest right you can have the same rate of forest loss in Colombia and Bolivia

um but because Brazil is just so much larger you're losing more land area at the same rate okay it's actually the

world's fifth largest country by land area okay

um so since 1970 about 700 000 square kilometers or 270 000 square miles of forest have been converted to other uses

so basically an area the size of Texas have been converted to other uses that is primarily agricultural

of that agriculture it is for ranching primarily cattle but some sheep

and some goat and then for plants we're talking mostly about soy and corn okay but those are the three largest

um um agricultural uses okay

Brazil doesn't just have the Amazon rainforest okay I'm obviously the Amazon rainforest exists in the Amazon River

basin there is a couple other rainforests um that are less well known in South

America including in Brazil but there's also the Atlantic Forest the Atlantic Forest is a very unique Forest that is

um biodiversity biodiversity and and the biodiversity sense it's very different from the the from the Amazon rainforest

the plants and animals that exist in the Atlantic Forest are very different from those in the Amazon rainforest okay only

about eight to fourteen percent of that Forest remains and the reason for that is because if I get rid of my markings

the Atlantic Forest is where most of Brazil's largest cities are it's very difficult to read on this map but most

of Brazil's large cities are on the Atlantic coast

okay so not only are we losing that Atlantic forest for agricultural use but we're also losing it for development

okay the Amazon rainforest though is huge about 80 percent of it Still Remains but

it is under threat so as people march further and further into the Amazon from every direction we lose more and more of

it every year but it is a very very very large Forest much of it Still Remains intact

okay so let's um contrast all this clear cutting with sustainable forestry so recall that

unsustainable use is using a natural resource at a rate greater than the rate that it can be replenished whereas

sustainable use is using that resource at a rate at or below the way the rate at which is replenished okay and then if

we break down the second part of this term forestry forestry is the science the practice the art of maintaining

forests and Woodlands okay it's basically managing forests that could include planting harvesting Timber

conserving the forest it could be using the forest for other non-wood means it's really used in the forest for any reason

and there is sustainable forestry and then there's unsustainable forestry and clear cutting is an example of

unsustainable Forestry some methods of sustainable forestry though Timber is a renewable resource if you manage it

properly so if you manage your Forest properly Timber is renewable right it grows right all you have to do is reseed

it it might take um 20 50 100 years for you to harvest that tree that you seed but your

grandkids at least can can Harvest it one method of sustainable forestry is selective cutting okay selective cutting

is harvesting trees based on pre-ordained conditions that could be that you reaches a tree of a certain

size it could be that you're only cutting trees of a certain age it could be that you're only cutting diseased

trees could be that you're only cutting trees that are windfall or harvesting trees that are windfall so trees that

are blown over in storms due to the wind or trees that are uprooted for any other reason

okay a lot of the forests in the United States are starting to only be used for especially the hardwood forest I should

say that the hardwood forest the oak Maple the Walnut the Birch all of that is typically

selectively cut in the United States now you won't clear cut Cherry because there's not enough Cherry in a forest to

clear cut it but you can selectively cut it and you would typically do that based off of

these characteristics and the most sustainable way would be to harvest windfall diseased or operated trees

trees that are going to die anyway okay um you can only buy from sustainable

certified programs so if you are buying wood or if you're buying any other Forest product if you're buying anything

that is grown in the tropical regions like palm oil or coconut or pineapples or anything

coffee you can look for some of these symbols one of those is Rainforest Alliance so you can look for the little

frog symbol one of them if you're just going for wood is the forest Stewardship Council

okay reusing wood is a great um way to not cut any more wood so you're reusing the wood that's already been cut

prohibiting login and ecologically sensitive or highly diverse areas okay so just

um if there's a lot of biodiversity an area just prohibit logging there okay this would be an example of

legislation uh reforestation or A4 station we'll talk about those on the next couple

slides but reforestation this part re is saying that there was force there previously it has been

clear-cut it's been otherwise Disturbed and you were reforesting that area you're converting it back into Forest

afforestation you're looking at a different root word that's essentially saying that you're taking a biome that

was previously not forest and now you're converting it to forests so you're planting Forest where there previously

was was not Forest before we'll talk about IPM or integrated Pest Management on another day we'll have an

entire day for IPM but part of this is going back to the selective cutting you're removing disease trees okay but

we'll talk about IPM on another day and we've already talked about prescribed burns when we talked about uh wildfires

in Colorado so I'm not really going to spend much time on that so we looked at Brazil for a negative

let's look at China for a positive um China is currently doing and has been for a while the largest A4 station

project in the world it's called their three North shelter Forest program but most people just refer to it as the

great green wall the goal of this was to stop the encroachment of the Gobi desert and Northern China

and so far about 500 000 square kilometers of forest have been planted and an area that was previously not

Forest that's the world that's making it the world's largest artificial Forest now there is a lot of problems and a lot

of criticisms with this um the labor used is often not um voluntary it's often conscripted

um the there's ecological problems um Beyond just the humanitarian problems um those ecological problems is that

many of these forests are monocultures they're for they're trees that grow very rapidly and then die

um possibly before reseeding themselves in this area that they're not native to

there's high tree mortality rates some of the places have up to 70 percent tree mortality rates so

um seven out of every 10 trees that you plant dies and then there's the depletion of

groundwater to water all these trees you notice the water lines all of these um lines are drip hoses to water these

trees they're obviously trying to plant trees and desert where trees typically don't grow so you have to give them a

lot of water that water has to come from somewhere and you don't have many rivers in the desert so it's coming from

groundwater but this is still a great example of aphorusation

and it is um stopping the encroachment of the of the Gobi

um the encroachment of the Gobi is basically due to the wind coming off of the Gobi and eroding the soil at the

edge of the at the edge of the of the desert creating more desert and then eroding the next layer of or the next

set of soil the next um you know soil boundary at the edge of that new desert creating more desert Etc so putting

trees there effectively holds that soil in place and stops that erosion okay we've already talked about

prescribed Burns um and a lot of detail when we talked about fire in Colorado so I'm going to skip this slide but if you

want to refresher you can pause it and read through it now and the same thing with this slide in

fact these slides are basically copied and pasted from what we talked about back in September

however I wanted to have them on there because they are an example of sustainable forestry and they are

specifically in the learning objectives so let's get to the learning objectives rather the Essential Knowledge for clear

cutting we talked about how clear cutting is economically advantageous that is typically in the short term

because once you have clear-cut that area you don't have any more trees to uh to cut down or to sell you have to wait

for them to regrow if you replant it okay so short-term economic benefits but it does have many problems

um that it causes soil erosion increased soil in the um sorry increased soil and stream

temperatures flooding all of the stuff that we've talked about okay um forests contain trees that absorb

pollutants and store carbon dioxide when you cut them down you release those pollutants well you don't release those

pollutants sorry that's wrong you just release the carbon dioxide the pollutants are typically fixed in

biological tissue and then they're not they're they're converted to some other form okay so like

um sulfates and the soil will be converted into proteins that have sulfur in them

okay so it's totally getting rid of the not getting rid of but chemically converting that pollutant but the carbon

dioxide though carbon dioxide is absorbed from the atmosphere locked in the biomass of the plants and then when

you cut them down you release that carbon dioxide through the process of decomposition or

combustion okay and then over to the sustainable

forestry the Essential Knowledge some of the methods of mitigating deforestation include reforestation using and buying

wood harvested by ecologically sustainable forestry techniques and reusing wood with reforestation I would

include afforestation in there as well okay methods to protect forests from pathogens and insects include IPM again

we'll talk about this on another day but you also have um The Selective removal of affected

trees okay so like we talked about when we talked about um the American chestnut if you see

affected trees you can cut them down so that they don't um so that they don't spread to other

trees now that was a failed technique with the American chestnut it didn't halt the um the the

spread of chestnut blight but it is still a technique that has worked in other situations

and then prescribed burning is another way that forests can be managed and that they can be managed

um sustainably okay so hope you guys found this interesting hope you learned something

I'll see you on class bye