Global Fires, the Amazon and Humans

May 23, 2012
By

(This article was first published on Graph of the Week, and kindly contributed to R-bloggers)

global annual co2 emissions map
Fires are natural - most of the time (click on image for larger view).

Natural Global Fires

Many plants and animals have evolved to depend on fires periodically occurring in certain parts of the world. This phenomenon has been occurring for millions of years, successfully replenishing and rejuvenating the areas in which it is allowed to happen. The ashes enrich the soil, animal populations are re-balanced and new life springs into existence. Additionally, these fires do not reduce the amount of land on which forests grow, thereby preserving the ecosystems contained within (with no loss of forest land).

Unnatural Global Fires

Using the word 'unnatural' is always risky, but here it is meant to convey control by humans - which in itself is 'natural', but introduces many variables not before seen in history. Unlike natural fires which are beneficial, unnatural forest fires often have the opposite effect - especially when used to clear land of trees to make way for agriculture or construction. Over time, the number of trees decreases while the number of humans increases. More humans require more agriculture which means more deforestation.
Carbon Dioxide

Carbon dioxide is a major product of wood combustion. Looking at the above map, the produced amounts of this gas from fire can be seen over a thirteen year period from 1997-2010 (click on the image for a larger view). It's fairly obvious that fires tend to arise in the same places year after year. In most cases, the carbon dioxide produced is a result of naturally occurring fires as described above. However, in a few cases - particularly the Amazon Rainforest - much of this carbon output arises from unnatural fires.

The Amazon Rainforest

What is so special about the Amazon rainforest? For starters, it represents over half of the world's remaining rainforests. It has been around for over 50 million years during which time numerous animals and plants have evolved and thrived within its confines. One in ten known species (of both plants and animals) lives in this area, representing a mind-boggling array of biodiversity. In a universe where life is scarce (see previous article about finding Earth II), the Amazon is brilliant diamond to be admired and respected.

Humans (nay, all animals) rely upon the rainforest as well. Not only does it produce oxygen, but it also consumes carbon dioxide - necessary for all breathing animals. NASA has estimated the number of trees world-wide at around 400 billion. The human population is nearly 7 billion which gives us around 57 trees per person. In the past, that ratio was much higher in favor of the trees. That being said, there are still enough trees to support the oxygen requirements for life as we know it presently, but the ratio is still going down.

Oxygen from Oceans

It should be noted that about half of the world's oxygen supply does not come from trees or plants, but from the phytoplankton in the world's oceans (which itself has changed, but that's another story for another time). That's a good thing, given the amount of deforestation which has occurred. Otherwise, we might already be able to notice tangible differences in our air.


yearly amazon deforestation rate graph
Brazil's GDP has gone up recently, perhaps reducing the need for deforestation.

Since 1970, about 80% of the Amazon rainforest remains. In terms of actual forest loss, that equates to about 745,000 square kilometers - that's larger than the size of France! However, as the chart above shows,  the rate of deforestation has been going down since 2004 due to a number of reasons. Hopefully this trend will continue - not only in the Amazon, but other forests as well.

Conclusion

Fires are a naturally occurring phenomenon which are beneficial to the world's ecosystems. However, when fire is used to remove forests for agriculture or construction, what remains has a greater burden to support a larger population of humans. This harms our symbiotic relationship with the trees so this cannot continue indefinitely. Like any good relationship, we must respect and nurture our partners while they do the same for us. Perhaps the recent trend in the Amazon is an indication that we understand this. Short-term gain is not a bad thing, but if it means a long-term loss then it is surely the wrong path.



Questions:
1) Will the Amazon rainforest be preserved?
2) What is going on in the world's oceans in terms of oxygen production?
3) When will a 'breaking point' occur at which time resources cannot support future population levels?

Data:
Code:
These graphs were generated using the 'ggplot2' and 'maps' packages within the R programming language. In the future, different plotting packages will begin to be seen here, including 3d plots and trellis plots. Stay tuned!

1st graph:
ggplot(countries, aes(long, lat, group=group)) +
    
    geom_polygon(data = global.carbon.1997.map.frame, aes(x=long, y=lat, fill=value, group=group), size=0.2) +
    geom_polygon(colour="black", alpha=0.2) +
    
    ylab("Latitude") +
    xlab("Longitude") +
    
    scale_fill_continuous(low="light grey", high="red",
        space = "Lab"
    ) +
    opts(title="1997 Global Carbon Emissions from Fire (1e12 grams Carbon per year)",
        legend.title = theme_blank(),
        panel.background = theme_blank())

2nd graph:
ggplot(amazon.frame, aes(x=Period, y=Annual_forest_loss)) +
    geom_point() +
    geom_line(aes(group=1),size=1.0) +
    geom_smooth(aes(group=1), method="lm", na.rm=FALSE, fill=NA, size=1.0) +
    
    ylab("Annual Forest Loss (square kilometers)") +
    xlab("Period") +
    opts(title="Amazon Deforestation Loss",
        axis.text.x=theme_text(angle=45, hjust=1),
        panel.background = theme_blank(),
        plot.margin = unit(c(0,6,0,0), "lines")) +
    scale_y_continuous(labels = mysep)
Further Reading:

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