Irrecoverable carbon in mountains and the global mitigation potential of agroforestry and increased tree cover in mountain agricultural systems

Robert J. Zomer; Jianbo Yang; Donatella Spano; Antonio Trabucco; Robert J. Zomer; Jianbo Yang; Donatella Spano; Antonio Trabucco

doi:10.48130/CAS-2023-0011

Figures (5) Tables (4)

Figure 1.
Global delineation of mountains and seven mountain categories, showing areal extent of mountains by region, and percent of area classified as mountains within each respective region. Source: UNEP-WCMC 'Mountains of the World'^[4,5].
Figure 2.
Manageable, vulnerable, and irrecoverable carbon with mountainous regions, in tons of carbon per hectare (tC·ha⁻¹), as per the year 2018^[18].
Figure 3.
Area of manageable, vulnerable, and irrecoverable carbon (km²) by region, and showing percent of that area classified as mountains (%)^[4,5,18].
Figure 4.
Biomass carbon on agricultural land with mountainous regions, by scenarios. Incremental change represented by two subsets of the first scenario: a) 10% increase in tree cover on all land under the median (50^th percentile) for each respective strata (n = 495), and b) increase of all land under the median up to the median. A systemic transformative change to a agroforestry type system incorporating increased tree cover as a core production component is represented by a range of percentiles (60^th−80^th) of tree cover for each respective strata, with the 70^th percentile assumed as an ecologically reasonable and attainable adoption level^{[5, 20, 41]}.
Figure 5.
Agricultural land found with areas classified as mountains, by regions. Total area of agriculture, mountains, and agriculture with mountains (millions km²) within each respective region are shown^[5,20].

Region	Manageable carbon		Vulnerable carbon		lrrecoverable carbon
Region	PgC	%	PgC	%	PgC	%
Asia Pacific	10.99	29.60	7.99	33.04	3.60	47.75
Central America	2.79	43.40	1.65	40.97	0.13	18.57
Central Asia	3.58	41.50	2.82	36.98	0.22	68.75
East Asia	28.03	80.86	17.50	80.79	1.38	72.63
Eastern and Southern Africa	15.78	29.12	9.84	28.08	1.98	35.74
Europe	10.86	33.00	6.14	32.00	2.33	32.45
North Africa	0.52	53.15	0.33	55.70	0.09	69.23
North America	40.66	32.92	22.08	33.43	6.85	35.38
Russia	28.21	24.02	10.90	20.77	4.91	15.52
South America	28.65	15.97	18.18	13.49	4.64	12.00
South Asia	5.68	64.36	3.42	64.40	0.47	61.84
Southeast Asia	21.59	48.62	14.86	44.83	3.72	32.86
West and Central Africa	5.84	8.16	3.90	7.37	0.61	5.33
Western Asia	4.89	86.14	2.55	86.00	0.25	80.65
Global	208.07	28.67	122.17	26.56	31.18	22.79

Table 1.

Irrecoverable, manageable, and vulnerable carbon (Pg C) globally, and as found within each of the respective mountain regions, and as a percentage (%) of the total carbon in each of the three categories of carbon found within each region^[4,5,18].

Region	Mean percent tree cover (%)							Area (km²)
Region	2000	2010	Change	50^th	60^th	70^th	80^th	Area (km²)
Asia Pacific	28.4	32.5	4.1	36.3	38.0	40.1	42.9	71,989
Central America	36.1	38.4	2.3	43.4	45.4	47.9	51.7	105,827
Central Asia	5.6	5.4	−0.3	6.4	7.0	8.0	9.6	194.908
East Asia	18.1	20.9	2.8	22.2	23.1	24.8	27.4	490,326
Eastern and Southern Africa	11.9	11.7	−0.2	12.8	13.4	14.3	16.2	605,705
Europe	14.6	16.7	2.1	18.1	19.2	20.8	23.7	294,482
North Africa	2.5	3.3	0.8	3.6	3.6	4.1	5.5	43,300
North America	30.2	29.6	−0.5	32.3	33.7	35.8	39.0	173,494
Russia	14.6	15	0.4	16.8	17.8	19.4	22.1	105,035
South America	23.5	26	2.5	28.3	29.9	32.5	36.9	501,408
South Asia	20.1	21.3	1.2	23.7	25.2	27.7	31.6	163,323
Southeast Asia	42.8	43.6	0.8	48.1	50.4	53.2	56.8	293,696
West and Central Africa	14.9	14	−1.0	15.4	16.3	17.7	20.5	147,633
Western Asia	5.5	6.3	0.8	7.4	8.0	9.0	11.0	476,485
Global	19.2	20.3	1.1	21.3	22.4	24.1	26.9	3,667,611

Table 2.

Mean tree cover (%) by percentile for all agricultural land globally, and within in the various mountainous regions. All land below the specified percentile threshold comes up to that level of adoption (percentile), and land already above the specified percentile remains as is^[5,20].

Region			Increase in biomass carbon by scenario and percentile (PgC)
	Biomass carbon (PgC)		Incremental		Systemic
	2000	2010	10%/Median	Median (50^th)	60^th	70^th	80^th
Asia Pacific	0.4	0.45	0.48	0.49	0.52	0.54	0.57
Central America	0.63	6.6	0.71	0.74	0.77	0.81	0.87
Central Asia	0.13	0.13	0.14	0.14	0.14	0.15	0.16
East Asia	0.89	0.99	1.03	1.03	1.06	1.11	1.19
Eastern and Southern Africa	0.9	0.9	0.94	0.95	0.98	1.02	1.12
Europe	0.34	0.37	0.37	0.38	0.40	0.43	0.47
North Africa	0.03	0.03	0.03	0.03	0.03	0.03	0.04
North America	0.7	0.69	0.73	0.73	0.76	0.80	0.86
Russia	0.08	0.08	0.08	0.08	0.09	0.09	0.10
South America	1.65	1.79	1.91	1.92	2.00	2.15	2.39
South Asia	0.37	0.38	0.41	0.41	0.43	0.46	0.52
Southeast Asia	2	2.07	2.21	2.31	2.42	2.56	2.73
West and Central Africa	0.39	0.37	0.41	0.4	0.42	0.45	0.51
Western Asia	0.41	0.43	0.39	0.4	0.42	0.47	0.53
Increased Biomass Carbon	/	0.43	0.52	0.67	1.10	1.73	2.71
Total Biomass Carbon	8.91	9.34	9.86	10.01	10.44	11.07	12.05

Table 3.

Biomass carbon on agricultural land within mountainous regions, by scenarios. Incremental change represented by two subsets of the first scenario: a) 10% increase in tree cover on all land under the median (50^th percentile) for each respective strata (n = 495), and b) increase of all land under the median up to the median. A systemic transformative change to a agroforestry type system incorporating increased tree cover as a core production component is represented by a range of percentiles (60^th−80^th) of tree cover for each respective strata, with the 70^th percentile assumed as an ecologically reasonable and attainable adoption level^[5,20,41].

		Increased biomass carbon (PgC)
		2010	1%	10%
Region	Asia Pacific	0.45	0.01	0.11
	Central America	0.66	0.02	0.16
	Central Asia	0.13	0.01	0.07
	East Asia	0.99	0.03	0.31
	Eastern and Southern Africa	0.9	0.04	0.44
	Europe	0.37	0.01	0.15
	North Africa	0.03	0.00	0.03
	North America	0.69	0.02	0.18
	Russia	0.08	0.00	0.02
	South America	1.79	0.06	0.57
	South Asia	0.38	0.01	0.13
	Southeast Asia	2.07	0.05	0.44
	West and Central Africa	0.37	0.02	0.15
	Western Asia	0.43	0.03	0.31
	Global	9.34	0.31	3.07
Country	China	0.918	0.030	0.297
	Brazil	0.769	0.031	0.290
	Ethiopia	0.410	0.021	0.208
	Indonesia	0.885	0.021	0.185
	Mexico	0.637	0.018	0.168
	Turkey	0.206	0.015	0.143
	Colombia	0.535	0.014	0.138
	Philippines	0.434	0.009	0.104
	India	0.251	0.009	0.098
	Spain	0.078	0.006	0.059
	Papua New Guinea	0.301	0.008	0.057
	Afghanistan	0.047	0.006	0.057
	Mongolia	0.090	0.005	0.049
	Peru	0.116	0.005	0.047
	lran	0.051	0.005	0.047
	Madagascar	0.178	0.004	0.044
	Honduras	0.168	0.005	0.040

Table 4.

Biomass carbon in 2010 (PgC), and potential increase in biomass carbon (PgC) on agricultural land within mountainous regions resulting from a 1% increase in tree cover, or shown as a 1% increase in tree cover per year for 10 years (10%), globally, by region, and by the top countries showing the highest potential biomass increase^[5,20,41].