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Energy Flowing Through the Ecosystem

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Chapters:

1. Ecosystems
2. Consumption
3. Population
4. Trophic Pyramid

Tables:

• Table 1. Percentage Global Land Cover Characteristics From AVHRR
• Table 2: Humanity's Increasing Energy Consumption

Figures:

• Figure 1. Biodiversity
• Figure 2. Global Land Cover Characteristics From AVHRR
• Figure 3: Human Appropriation of Net Primary Production
• Figure 4: Distribution of Net Primary Production
• Figure 5: Humanity's Consumption of Energy
• Figure 6: The Trophic Pyramid

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1. Ecosystems

After four and a half billion years of interdependencies, the life on Earth is a complex ecological system or ecosystem. As it turns out, some physical parameters make for greater quantities of life. A tropical rain forest is a good example. Other locations are almost barren of life, such as the Antarctic.

Biodiversity is a word that conveys the richness of the disparity of life. Land with many species and specimens has a high biodiversity. This occurs where energy is abundant and is readily mobile. Estuaries, tree tops and swamps have high biodiversity. Where there is little energy or little capacity to move energy about, there are few species and specimens.

Humans have usurped land with the richest supplies of energy. In so doing, they have removed the indigenous flora and fauna. This removal of the competition is a step in the direction of a future that allows only for life that provides a benefit to people. The following map provides and indication of our influence. It shows biodiversity hot spots; the richest and most threatened areas of the world.

Figure 1. Biodiversity Hot spots

Plans for the future can use land characteristics to determine energy levels. Associating ecosystems with land cover and with energy deposition can provide and indication of the amount of energy that is available and can be sustainably appropriated. The following map and table give and indication of our current knowledge.

Figure 2. Global Land Cover Characteristics From AVHRR

Table 1. Percentage Global Land Cover Characteristics From AVHRR

Id	Region	Area sq.m.	Cell count	percent
17	Antarctica	12955294896358.210938	975792	9.64%
20	Major Woods-Main Taiga	15571041627.412062	414	0.00%
21	Major Woods-Main Taiga	5538192477539.941406	139371	1.38%
22	Major Woods-Other Conifer	3102704024062.733887	60725	0.60%
23	Major Woods-Mixed: Decid & Evergrn Broad Lf with conifer	1536950883557.831299	31763	0.31%
24	Major Woods-Mixed: Decid & Evergrn Broad Lf with conifer	2007185848676.121094	30340	0.30%
25	Major Woods-Temp Broad Lf Forest	780287115971.479248	14759	0.15%
26	Major Woods-Temp Broad Lf Forest	712378712833.701538	11636	0.11%
27	Major Woods-Other Conifer	402802513310.048279	6546	0.06%
28	Interrupted Woods-Trop Montain:frst,grass,scrub,paramo,rock	1185786717748.041992	15459	0.15%
29	Major Woods-Trop/Subtrop Broad Lf Humid frst	6162632446114.984375	79817	0.79%
30	Non Woods-Cool/Cold Farms/Towns	2959862698549.866699	57507	0.57%
31	Non Woods-Warm/Hot Farms/Towns	9309647348894.322266	143007	1.41%
32	Major Woods-Trop/Subtrop Dry frst and Woodld	4714611523027.708984	61804	0.61%
33	Major Woods-Trop/Subtrop Broad Lf Humid frst	4250460429679.579102	54125	0.53%
36	Non Woods-Irrigated Paddylnd	1987885037439.005859	27453	0.27%
37	Non Woods-Other Irrigated Drylnd	1204215951987.350586	17621	0.17%
38	Non Woods-Other Irrigated Drylnd	284208608067.502075	4880	0.05%
39	Non Woods-Other Irrigated Drylnd	84052062887.436249	2007	0.02%
40	Non Woods-Main Cool Scrub & Grassld	3943879596164.254883	74347	0.73%
41	Non Woods-Main Warm/Hot Scrub & Grassld	17281753920109.261719	249837	2.47%
42	Non Woods-Tibetan, Siberian Cold Grass/Stunted Wood Complex	844962972873.480713	16607	0.16%
43	Interrupted Woods-Trop Savanna & Woodld	6717216465060.143555	87037	0.86%
44	Wetld/Coastal-Major Bog/Mire, Cool/Cold Climates	974049034298.122925	22510	0.22%
45	Wetld/Coastal-Major Warm/Hot Mangrove/Tropical Swamp Forest	1567705039505.850830	21278	0.21%
46	Interrupted Dry Woods-Mediterranean types	1001897102499.186401	15630	0.15%
47	Interrupted Dry Woods-Other Dry & Highld wds	2594651830663.824707	38087	0.38%
48	Interrupted Dry Woods-Semiarid Woodld & Low Frst	907562417199.618164	12612	0.12%
49	Non Woods-Nonpolar Sparse (rocky) Vegetation	16583263310.775343	222	0.00%
50	Non Woods-Nonpolar Sand Desert	5224729037072.687500	75477	0.75%
51	Non Woods-Other Nonpolar Desert & Semidesert	10945523633729.777344	157360	1.55%
52	Non Woods-Nonpolar Cool Semidesert Scrub	2001583803636.694824	36217	0.36%
53	Non Woods-Tundra	9393530849909.560547	270103	2.67%
54	Non Woods-Tundra	63252319789.794365	1218	0.01%
55	Interrupted Woods-Trop/Temp wds, Fields, Grass, Scrub	1213730638498.606445	24058	0.24%
56	Interrupted Woods-2nd grow Trop/sub Trop, Humid/temp/boreal frst	2901879848728.266602	44004	0.43%
57	Interrupted Woods-2nd grow Trop/sub Trop, Humid/temp/boreal frst	2237122005999.954102	42824	0.42%
58	Interrupted Woods-Trop/Temp wds, Fields, Grass, Scrub	2862917892459.063965	41620	0.41%
59	Interrupted Dry Woods-Succulent & thorn	3960416798810.236328	52661	0.52%
60	Major Woods-Southern Taiga	1141925938973.127930	26045	0.26%
61	Major Woods-Southern Taiga	454631805719.985657	9375	0.09%
62	Interrupted Woods-North/Maritime Taiga, subalpine	4353694475333.803223	123731	1.22%
63	Non Woods-Wooded Tundra Cold Grass/Stunted Wood Complex	1755574562241.592285	48608	0.48%
64	Non Woods-Heath & Moorland	150965279690.782806	2842	0.03%
65	Wetld/Coastal-Shore and Hinterland Complexes	346743177268.794556	5576	0.06%
66	Wetld/Coastal-Shore and Hinterland Complexes	271643838092.094574	4012	0.04%
67	Wetld/Coastal-Shore and Hinterland Complexes	227736876864.228302	3687	0.04%
68	Wetld/Coastal-Shore and Hinterland Complexes	158688278350.119598	2498	0.02%
69	Non Woods-Polar or Rock Desert	537498290159.993896	33652	0.33%
70	Non Woods-Ice	2200308405065.088379	107593	1.06%
71	Non Woods-Other Nonpolar Desert & Semidesert	92485282559.789078	1463	0.01%
*	no data	362524045849111.750000	6737183	66.54%

2. Consumption

Once we've exhausted the fossil fuels, we'll need to find our energy from other sources. Vegetation lies at the base of the ecosystem and it can provide energy whether wood for fires or fruit for eating. Vegetation is also refereed to as net primary production or NPP.

The following maps give an idea of the degree of impact that we have on the land surfaces of Earth. Obviously any appropriation that is greater than the rate of replenishment is not sustainable. If we use 100% or more of the net primary production, then the vegetation can not replenish and it will perish. Thus, it cannot collect any more energy from the Sun for us to use. The sustainable level of appropriation is likely much less than 100%. Yet, from the first map, we see that huge swathes of the most productive land are having their energy stores directed to human usage.

Today, the energy source is mainly fossil fuels. However, once they are exhausted we will need get our energy from elsewhere. Vegetation will become the most likely source. These maps show that this future is unsustainable hence would not make a good plan. Alternatives aren't obvious.

Human appropriation of net primary production (NPP) as a percentage of the local NPP.

Figure 3: Human appropriation of net primary production

Global distribution of resource consumption as measured by the amount of net primary production (NPP) appropriated by humans.

Figure 4: Distribution of net primary production

The news is no better for the ocean resources as shown in the following figure.

See National Center for Ecological Analysis and Synthesis.

3. Population

People need energy to power their bodies. This is biological energy. The more people that there are on Earth, the greater is their biological need. The following figure and table shows the increasing need based upon the standard 10 MJ energy per day requirement. This is about 3.65 x 10⁹ Joules per year.

Figure 5: Humanity's Consumption of Energy

The graph shows the story, the numbers give structure to any planning.

Table 2: Humanity's Increasing Energy Consumption

Values found on the U.S Census Bureau;

4. The Trophic Pyramid

Energy is essential for life on Earth. It flows through levels of the ecosystem. However, the flow is not very efficient. Even after millions of years of genetic improvements, there's still only about a 10% transfer of energy from one level of the pyramid to a higher level. The shape of a pyramid highlights this poor transfer rate but also highlights the dependence of one level to its supporting level underneath. The trophic pyramid is fundamental to life and is a valuable relation when considering energy allocations in the future.

The ecosystem's trophic pyramid is shown below.

Figure 6: The Trophic Pyramid

At the base of the pyramid are the autotrophs. These living things capture their energy needs directly from the Sun. Most of the plants about us are autotrophs. People are not as people cannot convert the Sun's radiation into a form that would power their bodies.

The next step up the pyramid is allocated to the herbivores. These creatures, munch on the plants. In so doing they capture their energy needs from the energy stores within the plants. Some people are pure vegetarians. Because of this, they live at this level of the trophic pyramid. Given the efficiencies of energy conversion, herbivores capture only about 10% of the plants energy stores.

The next step up the pyramid is allocated to the carnivores. These creatures, eat other animals. Some special cases like people and bears eat both vegetation and other animals. This merits giving them the name omnivore. Again because of efficiencies, meat eaters capture only about 10% of the energy stores in the herbivores. But this represents 1% of the original energy in the plants. Given this poor energy transfer efficiency, it is no wonder that carnivores are greatly outnumbered by herbivores who themselves are greatly outnumber by vegetation.

Sitting at the top of the pyramid are the tertiary consumers. These creatures feed on the carnivores. This seems unrealistic as most people believe that carnivores and more specifically, themselves, are at the top of the pyramid. However, there are huge quantities of tiny little creatures that feast on any dead creature. These are called saprotrophs. These little critters eat the dead which still contain large quantities of energy. As well, these creatures release the chemicals of the body so that they can be used in other bodies. Again considering efficiencies, only 10% of the dead creature or about 0.1% of the originating plant's energy is captured by the saprotrophs, yet their usefulness is unquestionable.

We know the total amount of energy and energy transfer efficiencies. With these we can calculate the maximum possible number of creatures at each level of the pyramid. This calculation facilitates future planning.

by Mark Foster Mortimer