Growing for good: producing a healthy, low greenhouse gas and water quality footprint diet in Aotearoa, New Zealand

Figures & data

Figure 1. Schematic outline of the process followed to create and test the two scenarios to achieve a healthy diet.

Table 1. Annual production, per hectare production required, and the crop areas required (and in addition to areas above current production) to grow the optimised healthy diet. Information is also given about the areas available for crop rotations, on average, within N and P pressure catchments. Refer to Table S3 for information on the crop rotations in major crop growing regions.

Land uses and crops	Production (t)	Current per ha production (t)	Area (ha) required for healthy diet (ha)	Area required above current production (ha)^a	Area provided by likely crop rotations within pressure catchments (ha)^b	Area provided by likely crop rotations outside of pressure catchments (ha)^b
Apples	358,477	61.0	5,877	−4,123	Na	Na
Broad beans	112,774	9.8	11,508	10,508	213,164	317,956
Carrots	91,682	85.0	1,079	−921	Na	Na
Dairy	84,253	1.2	72,867	−1,687,133	Na	Na
Oats	95,105	6.4	14,860	7,860	35,519	76,143
Onions	186,303	60.0	6,210	1,210	12,251	29,451
Citrus	325,204	35.0	9,292	7,292	−	7,292
Peas	207,543	9.0	23,060	9,060	213,164	317,956
Potatoes	689,652	65.0	10,610	610	3,423	8,755
Sheep/beef	8,036	0.3	26,785	−8,738,215	Na	Na
Wheat/barley	500,502	11.5	43,522	2,522	35,519	76,143

^a Negative values indicate that more area is already in production than required to meet the healthy diet.

^b These data are only for the targeted crop within a rotation. To calculate the total area occupied by the rotation, including non-target crops across New Zealand, divide the target crop area by 0.33, 0.37, 0.43, 0.43, 0.30, and 0.355 for Broad beans, Oats, Onions, Peas, Potatoes, and Wheat/Barley, respectively.

Table 2. Current area and the environment, production, and economic performance of agricultural product classes for a low GHG diet for New Zealand.

Crop class^a	Current area (km^2)	N loss (kg ha^−1 yr^−1)	P loss^b (kg ha^−1 yr^−1)	GHG loss (kg CO2-e ha^−1 yr^−1)	Production^c	Gross margin^d ($ ha^−1 yr^−1)	References
1-Dairy A	2,562	35	1.2	13330	1160	3,759	(Van der Weerden et al. 2018; Monaghan et al. 2021)
2-Dairy B	1,667	29	1.4	12881	1100	3,759	(Van der Weerden et al. 2018; Monaghan et al. 2021)
3-Dairy C	1,618	103	0.7	14506	1317	5,262	(Van der Weerden et al. 2018; Monaghan et al. 2021)
4-Dairy D	2,422	38	0.7	12492	1048	3,954	(Van der Weerden et al. 2018; Monaghan et al. 2021)
5-Sheep/beef A	10,334	8	0.5	448	1.4	199	(Hutchinson et al. 2019; Monaghan et al. 2021)
6-Sheep/beef B	7,920	17	1.1	3604	9.8	1392	(Hutchinson et al. 2019; Monaghan et al. 2021)
7-Sheep/beef C	8,714	5	0.3	2176	6.8	966	(Hutchinson et al. 2019; Monaghan et al. 2021)
8-Sheep/beef D	8,149	16	0.7	3714	10.1	1434	(Hutchinson et al. 2019; Monaghan et al. 2021)
9-Wheat	41	50	0.66	1643	11.5	2578	(Ryden et al. 1973; Barber et al. 2011; Norris et al. 2019)
10-Barley	56	28	0.12	1309	9.0	2064	(Evans 2002; Saunders et al. 2006; Norris et al. 2019)
11-Oats	7	74	0.33	1179	6.4	2286	(Ryden et al. 1973; Evans 2002; Rajaniemi et al. 2011; Norris et al. 2019)
12-Apple	10	18	0.48	673	61	18772	(Fenemor et al. 2015; Norris et al. 2019; Plant and Food Research 2019; Thomas et al. 2020)
13-Potato	10	88	0.16	1696	65	13050	(Norris et al. 2019; Plant and Food Research 2019; Thomas et al. 2020)
14-Onion	5	81	0.33	619	30	3053	(Norris et al. 2019; Plant and Food Research 2019; Thomas et al. 2020)
15-Peas	14	28	0.50	350	9	1080	(Norris et al. 2019; Plant and Food Research 2019; Thomas et al. 2020)
16-Carrot	2	30	0.13	431	85	3400	(Norris et al. 2019; Plant and Food Research 2019; Thomas et al. 2020)
17-Citrus	2	40	0.48	215	35	12872	(Tsushima et al. 2009; Plant and Food Research 2019; Thomas et al. 2020)
18-Bean	1	28	0.50	302	9.8	2830	(Evans 2002; Norris et al. 2019; Plant and Food Research 2019)
19-Plantation forestry	21,000	4	0.1	−25000	580	1150	(Cooper and Thomsen 1988; Davis 2014; Thomas et al. 2020)

^a Classes are designed to represent generic performance. Dairy A-D are sourced from Monaghan et al. (2021) for a Warm/Flat/Well drained/Moist typology in Waikato (A), Warm/Flat/Poorly-drained/Moist typology in Waikato (B), a Cool/Flat/Light soil/Irrigated typology in Canterbury (C), and a Cool/Flat/Well-drained/Moist typology in Southland. Sheep/beef A-D are sourced from Monaghan et al. (2021) for hill country typology in Marlborough-Canterbury (A), a hill country typology in Northland-Waikato-Bay of Plenty (B), a high country typology in Otago-Southland (C), and a finishing and breeding typology in Marlborough-Canterbury (D). Note that these typologies were compared and found to be similar to measured losses of N and P for the farm class (see Supplementary data in Monaghan et al. 2021).

^b Phosphorus losses for barley, potato, onions, peas, carrots, and beans are for subsurface flow only. Owing to a lack of data, P losses for apples are assumed to be the same as citrus.

^c Production is listed as stock units ha⁻¹ for dairy and sheep and beef classes and as t ha⁻¹ yr⁻¹ for all other crops. Production and gross margin for forestry were sourced from Farm Forestry New Zealand (nzffa.org.nz). Production data for arable crops are sourced from https://www.far.org.nz/assets/files/blog/files/c2bbd3c1-b18a-55dd-ba61-6126c8d5a939.pdf and from colleagues at the Foundation for Arable Research and Horticulture NZ.

^d Gross margins were sourced from Reynish (2020) for dairy, sheep and beef, wheat, barley, potatoes, and onions; the margin for apples were sourced from the Pipfruit Monitoring Programme (Ministry for Primary Industries 2017); the margin for oats came from the Foundation for Arable Research, while Horticulture New Zealand supplied margins for peas, carrot, citrus and beans. For sheep/beef classes A, B and D assume $142 per stock unit for Crossbred Ewe flock breeding own replacements, 155% lambing rate and $118 revenue per head, and $65.5 per head of beef cattle; sheep/beef class C assumes $142 per stock unit Merino Ewe flock breeding own replacements, $112 for meat and a 20-micron fleece for wool at $18.50 per head sold; Potato data are for the Agria variety.

Figure 2. Areas (ha) of different crops grown for both scenarios in catchments under pressure for nitrogen (top) and phosphorus (bottom). Note that these data are not adjusted for rotations. For example, a crop may only be grown in one out of four years and require times the area to meet targeted yield. Total cropland in catchments under N pressure for the climate and freshwater-focused scenarios were 37,693 and 46,862 ha, respectively, while areas under P pressure were 34,671 and 45,763 ha, respectively. To adjust individual crop areas to account for their production within a rotation across New Zealand, areas outside of pressure catchments can be adjusted for wheat and barley, oats, potatoes, onions, peas and beans by dividing by 0.355, 0.37, 0.30, 0.43, 0.43 and 0.33, respectively.

Figure 3. Percentage change across New Zealand in sheep and beef, dairy, forestry, and crops (adjusted for non-target crops in region-specific rotations) from current areas under both scenarios when focused on reducing nitrogen (top) or phosphorus (bottom). Current areas in sheep and beef, dairy, forestry, and cropland are 11.27, 2.24, 1.61, and 0.33 M ha, respectively.

Table 3. Effect of each scenario on the non-optimised percentage change in nitrogen and phosphorus load, greenhouse gas emissions and gross margin, in catchments under pressure from nitrogen and phosphorus and when these data are scaled up (along with land use changes outside pressure catchments) to the national level focusing on N or P. Values in parentheses are the standard error calculated from regional values.

Area and scenario	Nitrogen load	Phosphorus load	Greenhouse gas emissions	Gross margin
N pressure catchments only
Climate focused	−17.7 (3.0)	−31.8 (4.3)	−535 (408)	1.3 (4.3)
Freshwater focused	−43.6 (5.3)	−50.2 (6.7)	−566 (302)	−8.9 (7.6)
P pressure catchments only
Climate focused	−20.9 (3.1)	−34.6 (4.6)	−824 (113)	0.5 (4.5)
Freshwater focused	−35.3 (6.0)	−55.1 (7.4)	−369 (132)	−8.3 (8.3)
National – N focus
Climate focused	−6.0 (1.6)	−9.9 (2.3)	−260 (176)	0.4 (1.7)
Freshwater focused	−12.7 (2.5)	−12.9 (2.8)	−336 (205)	−2.4 (2.6)
National – P focus
Climate focused	−7.1 (2.0)	−12.3 (3.1)	−348 (238)	0.2 (2.6)
Freshwater focused	−6.1 (1.7)	−9.7 (2.2)	−183 (59)	−1.4 (1.2)

Table 4. Effect of land use change on absolute ($M) gross margin in pressure catchments focusing on N or P.

Scenario	Cropland	Dairy	Sheep and Beef	Forestry	Sum difference
N focus
Climate focused	158	−702	−1,288	1,921	89
Freshwater focused	144	−1,466	−1,607	2,402	−526
P focus
Climate focused	155	−786	−1,897	2,571	42
Freshwater focused	145	−744	−1,242	1,526	−315

Figure 4. Effect of each scenario on the percentage change in nitrogen and phosphorus load, greenhouse gas emissions and gross margin in catchments under pressure from nitrogen in each region. The least significant difference at the P < 0.05 level is given for the contrast of regional means for both scenarios. Values refer to absolute estimated change in gross margin (millions NZD). Note that some decreases in greenhouse gas emissions exceed the y-axis scale.

Figure 5. Effect of each scenario on the percentage change in nitrogen and phosphorus load, greenhouse gas emissions and gross margin in catchments under pressure from phosphorus in each region. The least significant difference at the P < 0.05 level is given for the contrast of regional means for both scenarios. Values refer to absolute estimated change in gross margin (millions NZD).

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Data availability statement

The supplementary data that support the findings of this study are openly available in figshare at https://doi.org/10.6084/m9.figshare.16614124.